diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 36fcbe7..a294045 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -12,8 +12,10 @@ jobs:
       fail-fast: true
       matrix:
         php:
-          - '8.0'
           - '8.1'
+          - '8.2'
+          - '8.3'
+          - '8.4'
 
     name: PHP ${{ matrix.php }}
 
@@ -38,3 +40,9 @@ jobs:
 
       - name: Run static analysis
         run: composer run-script phpstan
+
+      - name: Run rector
+        run: composer run-script rector-dry-run
+
+      - name: Run phpcs analysis
+        run: composer run-script phpcs
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4b99b1a..e8410db 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [4.0.0] - 2024-01-04
+### Changed
+- Switch to PHP 8.1
+
 ## [3.2.0] - 2022-03-05
 ### Added
 - Base Apache Cassandra support
diff --git a/composer.json b/composer.json
index f0e12ee..e833a2a 100644
--- a/composer.json
+++ b/composer.json
@@ -10,17 +10,18 @@
     "plantuml"
   ],
   "require": {
-    "php": ">=8.0",
+    "php": ">=8.1",
     "ext-json": "*",
-    "symfony/console": "^3.0|^4.0|^5.0|^6.0",
-    "twig/twig": "^2.0"
+    "symfony/console": "^5.0||^6.0",
+    "twig/twig": "^3.0"
   },
   "require-dev": {
-    "roave/security-advisories": "dev-master",
-    "phpunit/phpunit": "^9.0",
-    "squizlabs/php_codesniffer": "^3.0",
-    "slevomat/coding-standard": "^7.0",
-    "phpstan/phpstan": "^1.4"
+    "phpstan/phpstan": "^2.0",
+    "phpunit/phpunit": "^10.0",
+    "rector/rector": "^2.0",
+    "roave/security-advisories": "dev-latest",
+    "slevomat/coding-standard": "^8.0",
+    "squizlabs/php_codesniffer": "^3.0"
   },
   "autoload": {
     "psr-4": {
@@ -36,9 +37,11 @@
     "database-schema-visualization"
   ],
   "scripts": {
-    "phpcs": "phpcs --standard=PSR12",
-    "phpstan": "phpstan analyse",
-    "test": "php ./vendor/bin/phpunit"
+    "phpcs": "phpcs",
+    "phpstan": "phpstan analyse --memory-limit=512M",
+    "test": "php ./vendor/bin/phpunit",
+    "rector": "php ./vendor/bin/rector process example src test",
+    "rector-dry-run": "php ./vendor/bin/rector process example src test --dry-run"
   },
   "config": {
     "allow-plugins": {
diff --git a/example/code/image.php b/example/code/image.php
index 7fffd85..b3f0d5c 100644
--- a/example/code/image.php
+++ b/example/code/image.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\ConnectionCollection;
 use Pongee\DatabaseSchemaVisualization\Export\Plantuml;
diff --git a/example/code/json.php b/example/code/json.php
index 0160371..9ead915 100644
--- a/example/code/json.php
+++ b/example/code/json.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\ConnectionCollection;
 use Pongee\DatabaseSchemaVisualization\Export\Json;
diff --git a/example/code/plantuml.php b/example/code/plantuml.php
index 76ed296..1c0f1e8 100644
--- a/example/code/plantuml.php
+++ b/example/code/plantuml.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\ConnectionCollection;
 use Pongee\DatabaseSchemaVisualization\Export\Plantuml;
diff --git a/phpcs.xml b/phpcs.xml
index 126d61b..0f705ba 100644
--- a/phpcs.xml
+++ b/phpcs.xml
@@ -1,21 +1,10 @@
 <?xml version="1.0"?>
 <ruleset>
-	<config name="testVersion" value="7.1-"/>
 	<arg name="colors"/>
 
 	<file>src</file>
 	<file>test</file>
+	<file>example</file>
 
-    <rule ref="PSR2"/>
-	<rule ref="Generic.Arrays.DisallowLongArraySyntax.Found"/>
-
-	<config name="installed_paths" value="../../slevomat/coding-standard"/>
-	<rule ref="SlevomatCodingStandard.TypeHints.DeclareStrictTypes">
-		<properties>
-			<property name="newlinesCountBetweenOpenTagAndDeclare" value="0"/>
-			<property name="spacesCountAroundEqualsSign" value="0"/>
-		</properties>
-	</rule>
-	<rule ref="SlevomatCodingStandard.Namespaces.AlphabeticallySortedUses"/>
-	<rule ref="SlevomatCodingStandard.TypeHints.ReturnTypeHintSpacing"/>
+	<rule ref="PSR12"></rule>
 </ruleset>
diff --git a/phpstan.neon.dist b/phpstan.neon
similarity index 93%
rename from phpstan.neon.dist
rename to phpstan.neon
index 464566f..016866b 100644
--- a/phpstan.neon.dist
+++ b/phpstan.neon
@@ -16,7 +16,3 @@ parameters:
 
     fileExtensions:
         - php
-
-    excludes_analyse:
-        - vendor
-
diff --git a/rector.php b/rector.php
new file mode 100644
index 0000000..a26fbd0
--- /dev/null
+++ b/rector.php
@@ -0,0 +1,24 @@
+<?php
+
+declare(strict_types=1);
+use Rector\Config\RectorConfig;
+use Rector\DeadCode\Rector\ClassMethod\RemoveUselessParamTagRector;
+use Rector\DeadCode\Rector\ClassMethod\RemoveUselessReturnTagRector;
+use Rector\DeadCode\Rector\Node\RemoveNonExistingVarAnnotationRector;
+use Rector\DeadCode\Rector\Property\RemoveUselessReadOnlyTagRector;
+use Rector\DeadCode\Rector\Property\RemoveUselessVarTagRector;
+
+return RectorConfig::configure()
+    ->withRules([
+        RemoveUselessParamTagRector::class,
+        RemoveUselessReturnTagRector::class,
+        RemoveUselessReadOnlyTagRector::class,
+        RemoveNonExistingVarAnnotationRector::class,
+        RemoveUselessVarTagRector::class,
+    ])
+    ->withPreparedSets(
+        typeDeclarations: true,
+    )
+    ->withPhpSets(
+        php81: true,
+    );
\ No newline at end of file
diff --git a/src/Command/Mysql/MysqlCommandAbstract.php b/src/Command/Mysql/MysqlCommandAbstract.php
index 48a01e0..45d179c 100644
--- a/src/Command/Mysql/MysqlCommandAbstract.php
+++ b/src/Command/Mysql/MysqlCommandAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Command\Mysql;
 
@@ -16,15 +18,11 @@ abstract class MysqlCommandAbstract extends Command
     protected const ARGUMENT_FILE = 'file';
     protected const OPTION_CONNECTION = 'connection';
 
-    protected ParserInterface $parser;
-
     protected string $rootDir;
 
-    public function __construct(ParserInterface $parser, string $rootDir)
+    public function __construct(protected ParserInterface $parser, string $rootDir)
     {
         parent::__construct();
-
-        $this->parser = $parser;
         $this->rootDir = rtrim($rootDir, DIRECTORY_SEPARATOR) . DIRECTORY_SEPARATOR;
 
         $this
@@ -103,9 +101,10 @@ protected function getForcedConnections(array $connections): ConnectionCollectio
                 \.
                 (?<parentTableColumns>[^.]+)
                 $
-            #x', $connection, $matches);
+            #x', (string) $connection, $matches);
 
-            if (!empty($matches['childTableName'])
+            if (
+                !empty($matches['childTableName'])
                 && !empty($matches['childTableColumns'])
                 && !empty($matches['parentTableName'])
                 && !empty($matches['parentTableColumns'])
diff --git a/src/Command/Mysql/MysqlImageCommand.php b/src/Command/Mysql/MysqlImageCommand.php
index d99cc8b..ce40990 100644
--- a/src/Command/Mysql/MysqlImageCommand.php
+++ b/src/Command/Mysql/MysqlImageCommand.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Command\Mysql;
 
diff --git a/src/Command/Mysql/MysqlJsonCommand.php b/src/Command/Mysql/MysqlJsonCommand.php
index 864158c..9cb475d 100644
--- a/src/Command/Mysql/MysqlJsonCommand.php
+++ b/src/Command/Mysql/MysqlJsonCommand.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Command\Mysql;
 
diff --git a/src/Command/Mysql/MysqlPlantumlCommand.php b/src/Command/Mysql/MysqlPlantumlCommand.php
index f0a5b1d..25d0066 100644
--- a/src/Command/Mysql/MysqlPlantumlCommand.php
+++ b/src/Command/Mysql/MysqlPlantumlCommand.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Command\Mysql;
 
diff --git a/src/DataObject/Sql/Database/Connection/ConnectionAbstract.php b/src/DataObject/Sql/Database/Connection/ConnectionAbstract.php
index 3b8ac3e..3c13e08 100644
--- a/src/DataObject/Sql/Database/Connection/ConnectionAbstract.php
+++ b/src/DataObject/Sql/Database/Connection/ConnectionAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/ConnectionCollection.php b/src/DataObject/Sql/Database/Connection/ConnectionCollection.php
index 6eadf41..bf7ec5e 100644
--- a/src/DataObject/Sql/Database/Connection/ConnectionCollection.php
+++ b/src/DataObject/Sql/Database/Connection/ConnectionCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/ConnectionCollectionInterface.php b/src/DataObject/Sql/Database/Connection/ConnectionCollectionInterface.php
index 93cff6a..a1fc70d 100644
--- a/src/DataObject/Sql/Database/Connection/ConnectionCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Connection/ConnectionCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/ConnectionInterface.php b/src/DataObject/Sql/Database/Connection/ConnectionInterface.php
index 5681531..264403c 100644
--- a/src/DataObject/Sql/Database/Connection/ConnectionInterface.php
+++ b/src/DataObject/Sql/Database/Connection/ConnectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/ConnectionIterator.php b/src/DataObject/Sql/Database/Connection/ConnectionIterator.php
index 583b000..0b471b1 100644
--- a/src/DataObject/Sql/Database/Connection/ConnectionIterator.php
+++ b/src/DataObject/Sql/Database/Connection/ConnectionIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/NotDefinedConnection.php b/src/DataObject/Sql/Database/Connection/NotDefinedConnection.php
index eb42a8c..dc4b904 100644
--- a/src/DataObject/Sql/Database/Connection/NotDefinedConnection.php
+++ b/src/DataObject/Sql/Database/Connection/NotDefinedConnection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/OneToManyConnection.php b/src/DataObject/Sql/Database/Connection/OneToManyConnection.php
index 398b048..d64ee0d 100644
--- a/src/DataObject/Sql/Database/Connection/OneToManyConnection.php
+++ b/src/DataObject/Sql/Database/Connection/OneToManyConnection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Connection/OneToOneConnection.php b/src/DataObject/Sql/Database/Connection/OneToOneConnection.php
index 227e02a..8f82911 100644
--- a/src/DataObject/Sql/Database/Connection/OneToOneConnection.php
+++ b/src/DataObject/Sql/Database/Connection/OneToOneConnection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection;
 
diff --git a/src/DataObject/Sql/Database/Table.php b/src/DataObject/Sql/Database/Table.php
index 5472962..bf76d64 100644
--- a/src/DataObject/Sql/Database/Table.php
+++ b/src/DataObject/Sql/Database/Table.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database;
 
@@ -23,17 +25,17 @@ class Table implements TableInterface
 {
     private string $name = '';
 
-    private ColumnCollectionInterface|ColumnCollection $columns;
+    private readonly ColumnCollectionInterface|ColumnCollection $columns;
 
     private ?PrimaryKeyInterface $primaryKey = null;
 
-    private SimpleIndexCollection|SimpleIndexCollectionInterface $simpleIndexes;
+    private readonly SimpleIndexCollection|SimpleIndexCollectionInterface $simpleIndexes;
 
-    private UniqueIndexCollectionInterface|UniqueIndexCollection $uniqueIndexes;
+    private readonly UniqueIndexCollectionInterface|UniqueIndexCollection $uniqueIndexes;
 
-    private FulltextIndexCollectionInterface|FulltextIndexCollection $fulltextIndexes;
+    private readonly FulltextIndexCollectionInterface|FulltextIndexCollection $fulltextIndexes;
 
-    private SpatialIndexCollection|SpatialIndexCollectionInterface $spatialIndexes;
+    private readonly SpatialIndexCollection|SpatialIndexCollectionInterface $spatialIndexes;
 
     public function __construct()
     {
diff --git a/src/DataObject/Sql/Database/Table/Column.php b/src/DataObject/Sql/Database/Table/Column.php
index 0af654d..e5f58bb 100644
--- a/src/DataObject/Sql/Database/Table/Column.php
+++ b/src/DataObject/Sql/Database/Table/Column.php
@@ -1,15 +1,17 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 
 class Column implements ColumnInterface
 {
     public function __construct(
-        private string $name,
-        private string $type,
-        private array $typeParameters,
-        private string $otherParameters,
-        private string $comment
+        private readonly string $name,
+        private readonly string $type,
+        private readonly array $typeParameters,
+        private readonly string $otherParameters,
+        private readonly string $comment
     ) {
     }
 
diff --git a/src/DataObject/Sql/Database/Table/ColumnCollection.php b/src/DataObject/Sql/Database/Table/ColumnCollection.php
index caef972..9f1768e 100644
--- a/src/DataObject/Sql/Database/Table/ColumnCollection.php
+++ b/src/DataObject/Sql/Database/Table/ColumnCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 
@@ -7,7 +9,7 @@ class ColumnCollection implements ColumnCollectionInterface
     /** @var ColumnInterface[] */
     private array $columns = [];
 
-    public function add(ColumnInterface $column)
+    public function add(ColumnInterface $column): void
     {
         $this->columns[$column->getName()] = $column;
     }
diff --git a/src/DataObject/Sql/Database/Table/ColumnCollectionInterface.php b/src/DataObject/Sql/Database/Table/ColumnCollectionInterface.php
index d3d80b2..cc33cfa 100644
--- a/src/DataObject/Sql/Database/Table/ColumnCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Table/ColumnCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 
diff --git a/src/DataObject/Sql/Database/Table/ColumnInterface.php b/src/DataObject/Sql/Database/Table/ColumnInterface.php
index 063986f..aca100e 100644
--- a/src/DataObject/Sql/Database/Table/ColumnInterface.php
+++ b/src/DataObject/Sql/Database/Table/ColumnInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 
diff --git a/src/DataObject/Sql/Database/Table/ColumnIterator.php b/src/DataObject/Sql/Database/Table/ColumnIterator.php
index 20086b4..4d67281 100644
--- a/src/DataObject/Sql/Database/Table/ColumnIterator.php
+++ b/src/DataObject/Sql/Database/Table/ColumnIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/FulltextIndex.php b/src/DataObject/Sql/Database/Table/Index/FulltextIndex.php
index 8ee0a45..f2cc7a1 100644
--- a/src/DataObject/Sql/Database/Table/Index/FulltextIndex.php
+++ b/src/DataObject/Sql/Database/Table/Index/FulltextIndex.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollection.php b/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollection.php
index 7f5e904..982bac1 100644
--- a/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollection.php
+++ b/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionInterface.php b/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionInterface.php
index b55821a..3ec1cf6 100644
--- a/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/FulltextIndexInterface.php b/src/DataObject/Sql/Database/Table/Index/FulltextIndexInterface.php
index eafdc93..7f95e97 100644
--- a/src/DataObject/Sql/Database/Table/Index/FulltextIndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/FulltextIndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/FulltextIndexIterator.php b/src/DataObject/Sql/Database/Table/Index/FulltextIndexIterator.php
index 7fab12d..608891d 100644
--- a/src/DataObject/Sql/Database/Table/Index/FulltextIndexIterator.php
+++ b/src/DataObject/Sql/Database/Table/Index/FulltextIndexIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/IndexAbstract.php b/src/DataObject/Sql/Database/Table/Index/IndexAbstract.php
index 2985505..e59151e 100644
--- a/src/DataObject/Sql/Database/Table/Index/IndexAbstract.php
+++ b/src/DataObject/Sql/Database/Table/Index/IndexAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/IndexInterface.php b/src/DataObject/Sql/Database/Table/Index/IndexInterface.php
index 896d567..5f2e00a 100644
--- a/src/DataObject/Sql/Database/Table/Index/IndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/IndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php b/src/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
index e43e712..f8cbc9d 100644
--- a/src/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
+++ b/src/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/NamedIndexInterface.php b/src/DataObject/Sql/Database/Table/Index/NamedIndexInterface.php
index eef5d5f..9f16de6 100644
--- a/src/DataObject/Sql/Database/Table/Index/NamedIndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/NamedIndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/PrimaryKey.php b/src/DataObject/Sql/Database/Table/Index/PrimaryKey.php
index 9d9ca4d..8387c47 100644
--- a/src/DataObject/Sql/Database/Table/Index/PrimaryKey.php
+++ b/src/DataObject/Sql/Database/Table/Index/PrimaryKey.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/PrimaryKeyInterface.php b/src/DataObject/Sql/Database/Table/Index/PrimaryKeyInterface.php
index 2e1eeb2..363ed61 100644
--- a/src/DataObject/Sql/Database/Table/Index/PrimaryKeyInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/PrimaryKeyInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SimpleIndex.php b/src/DataObject/Sql/Database/Table/Index/SimpleIndex.php
index 7d3e63a..1df0f09 100644
--- a/src/DataObject/Sql/Database/Table/Index/SimpleIndex.php
+++ b/src/DataObject/Sql/Database/Table/Index/SimpleIndex.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollection.php b/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollection.php
index 001b912..a8cae0a 100644
--- a/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollection.php
+++ b/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionInterface.php b/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionInterface.php
index df1888b..7425505 100644
--- a/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SimpleIndexInterface.php b/src/DataObject/Sql/Database/Table/Index/SimpleIndexInterface.php
index 0979e00..ff2a923 100644
--- a/src/DataObject/Sql/Database/Table/Index/SimpleIndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/SimpleIndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SimpleIndexIterator.php b/src/DataObject/Sql/Database/Table/Index/SimpleIndexIterator.php
index 62da629..6ad16f2 100644
--- a/src/DataObject/Sql/Database/Table/Index/SimpleIndexIterator.php
+++ b/src/DataObject/Sql/Database/Table/Index/SimpleIndexIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SpatialIndex.php b/src/DataObject/Sql/Database/Table/Index/SpatialIndex.php
index eaa67a1..ac733e4 100644
--- a/src/DataObject/Sql/Database/Table/Index/SpatialIndex.php
+++ b/src/DataObject/Sql/Database/Table/Index/SpatialIndex.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollection.php b/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollection.php
index 2ee6579..f595968 100644
--- a/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollection.php
+++ b/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionInterface.php b/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionInterface.php
index 81ca351..454dab6 100644
--- a/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SpatialIndexInterface.php b/src/DataObject/Sql/Database/Table/Index/SpatialIndexInterface.php
index ac12397..6f44d33 100644
--- a/src/DataObject/Sql/Database/Table/Index/SpatialIndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/SpatialIndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/SpatialIndexIterator.php b/src/DataObject/Sql/Database/Table/Index/SpatialIndexIterator.php
index 5661ac6..1e2abf3 100644
--- a/src/DataObject/Sql/Database/Table/Index/SpatialIndexIterator.php
+++ b/src/DataObject/Sql/Database/Table/Index/SpatialIndexIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/UniqueIndex.php b/src/DataObject/Sql/Database/Table/Index/UniqueIndex.php
index b1312fb..a7fb6a8 100644
--- a/src/DataObject/Sql/Database/Table/Index/UniqueIndex.php
+++ b/src/DataObject/Sql/Database/Table/Index/UniqueIndex.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollection.php b/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollection.php
index 1b5668a..f114991 100644
--- a/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollection.php
+++ b/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionInterface.php b/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionInterface.php
index a66570d..ea8a3ce 100644
--- a/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/UniqueIndexInterface.php b/src/DataObject/Sql/Database/Table/Index/UniqueIndexInterface.php
index 178bca0..0f3068b 100644
--- a/src/DataObject/Sql/Database/Table/Index/UniqueIndexInterface.php
+++ b/src/DataObject/Sql/Database/Table/Index/UniqueIndexInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/Table/Index/UniqueIndexIterator.php b/src/DataObject/Sql/Database/Table/Index/UniqueIndexIterator.php
index 12f1079..0e6d374 100644
--- a/src/DataObject/Sql/Database/Table/Index/UniqueIndexIterator.php
+++ b/src/DataObject/Sql/Database/Table/Index/UniqueIndexIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Index;
 
diff --git a/src/DataObject/Sql/Database/TableCollection.php b/src/DataObject/Sql/Database/TableCollection.php
index 054c828..fad7948 100644
--- a/src/DataObject/Sql/Database/TableCollection.php
+++ b/src/DataObject/Sql/Database/TableCollection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database;
 
diff --git a/src/DataObject/Sql/Database/TableCollectionInterface.php b/src/DataObject/Sql/Database/TableCollectionInterface.php
index c924e4c..6edda6e 100644
--- a/src/DataObject/Sql/Database/TableCollectionInterface.php
+++ b/src/DataObject/Sql/Database/TableCollectionInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database;
 
diff --git a/src/DataObject/Sql/Database/TableInterface.php b/src/DataObject/Sql/Database/TableInterface.php
index 7799ad1..8b643e1 100644
--- a/src/DataObject/Sql/Database/TableInterface.php
+++ b/src/DataObject/Sql/Database/TableInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database;
 
diff --git a/src/DataObject/Sql/Database/TableIterator.php b/src/DataObject/Sql/Database/TableIterator.php
index b128203..05082e9 100644
--- a/src/DataObject/Sql/Database/TableIterator.php
+++ b/src/DataObject/Sql/Database/TableIterator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database;
 
diff --git a/src/DataObject/Sql/Schema.php b/src/DataObject/Sql/Schema.php
index f3be26f..85b293e 100644
--- a/src/DataObject/Sql/Schema.php
+++ b/src/DataObject/Sql/Schema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql;
 
diff --git a/src/DataObject/Sql/SchemaInterface.php b/src/DataObject/Sql/SchemaInterface.php
index 4aa4bac..f946b38 100644
--- a/src/DataObject/Sql/SchemaInterface.php
+++ b/src/DataObject/Sql/SchemaInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\DataObject\Sql;
 
diff --git a/src/Export/ExportInterface.php b/src/Export/ExportInterface.php
index 849e1f7..34a3599 100644
--- a/src/Export/ExportInterface.php
+++ b/src/Export/ExportInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Export;
 
diff --git a/src/Export/Json.php b/src/Export/Json.php
index eff3a2b..bd60379 100644
--- a/src/Export/Json.php
+++ b/src/Export/Json.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Export;
 
diff --git a/src/Export/Plantuml.php b/src/Export/Plantuml.php
index 7fcee4a..3a4657f 100644
--- a/src/Export/Plantuml.php
+++ b/src/Export/Plantuml.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Export;
 
diff --git a/src/Generator/ImageGenerator.php b/src/Generator/ImageGenerator.php
index cd4714c..c8b6eb9 100644
--- a/src/Generator/ImageGenerator.php
+++ b/src/Generator/ImageGenerator.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Generator;
 
@@ -15,16 +17,13 @@ class ImageGenerator
     protected Environment $twig;
 
     public function __construct(
-        private string $imageType,
-        private string $plantumlJarPath,
-        private string $outputFolder
+        private readonly string $imageType,
+        private readonly string $plantumlJarPath,
+        private readonly string $outputFolder
     ) {
     }
 
     /**
-     * @param string $plantuml
-     *
-     * @return string
      * @throws Exception
      */
     public function generate(string $plantuml): string
@@ -57,11 +56,6 @@ public function generate(string $plantuml): string
         return $plantumlPng;
     }
 
-    /**
-     * @param SplFileObject $sourceFile
-     *
-     * @return string
-     */
     private function generatePlantuml(SplFileObject $sourceFile): string
     {
         exec(
diff --git a/src/Parser/CassandraParser.php b/src/Parser/CassandraParser.php
index dedf323..f89b772 100644
--- a/src/Parser/CassandraParser.php
+++ b/src/Parser/CassandraParser.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Parser;
 
@@ -37,8 +39,7 @@ class CassandraParser extends ParserAbstract
     public function run(
         string $nativeSqlSchema,
         ConnectionCollectionInterface $forcedConnectionCollection
-    ): SchemaInterface
-    {
+    ): SchemaInterface {
         $runResult = parent::run($nativeSqlSchema, $forcedConnectionCollection);
         $this->handleMapAndSetConnections($runResult->getTables(), $runResult->getConnections());
         return $runResult;
@@ -218,9 +219,7 @@ protected function getColumnsWithoutRequiredTypeParametersFromCreateTableSchema(
     protected function trimNames(string ...$strings): array
     {
         return array_map(
-            function ($string) {
-                return $this->trimName($string);
-            },
+            fn($string): string => $this->trimName($string),
             $strings
         );
     }
@@ -228,9 +227,7 @@ function ($string) {
     protected function getFormatedParameters(string ...$strings): array
     {
         return array_map(
-            function ($string) {
-                return $this->getFormatedParameter($string);
-            },
+            fn($string): string => $this->getFormatedParameter($string),
             $strings
         );
     }
@@ -532,21 +529,22 @@ public function getConnectionsByCreateTable(string $sql): ConnectionCollectionIn
     private function handleMapAndSetConnections(
         TableCollection $tables,
         ConnectionCollectionInterface $connections
-    ) : ConnectionCollection
-    {
+    ): ConnectionCollection {
         $allDefinedTables = array_map(
-            function (TableInterface $table) {
-                return $table->getName();
-            },
+            fn(TableInterface $table): string => $table->getName(),
             $tables->getIterator()->getArrayCopy()
         );
 
         foreach ($tables as $table) {
             foreach ($table->getColumns() as $column) {
-                if (!in_array($column->getType(), ['set', 'map', 'frozen'])) continue;
+                if (!in_array($column->getType(), ['set', 'map', 'frozen'])) {
+                    continue;
+                }
 
                 foreach ($column->getTypeParameters() as $typeParameter) {
-                    if (!isset($allDefinedTables[$typeParameter])) continue;
+                    if (!isset($allDefinedTables[$typeParameter])) {
+                        continue;
+                    }
                     $connections->add(new OneToManyConnection($table->getName(), $typeParameter, [], []));
                 }
             }
diff --git a/src/Parser/MysqlParser.php b/src/Parser/MysqlParser.php
index 880fe68..faa216b 100644
--- a/src/Parser/MysqlParser.php
+++ b/src/Parser/MysqlParser.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Parser;
 
@@ -182,9 +184,7 @@ protected function getColumnsWithoutRequiredTypeParametersFromCreateTableSchema(
     protected function trimNames(string ...$strings): array
     {
         return array_map(
-            function ($string) {
-                return $this->trimName($string);
-            },
+            fn($string): string => $this->trimName($string),
             $strings
         );
     }
@@ -192,9 +192,7 @@ function ($string) {
     protected function getFormatedParameters(string ...$strings): array
     {
         return array_map(
-            function ($string) {
-                return $this->getFormatedParameter($string);
-            },
+            fn($string): string => $this->getFormatedParameter($string),
             $strings
         );
     }
diff --git a/src/Parser/ParserAbstract.php b/src/Parser/ParserAbstract.php
index 84a938b..89b4374 100644
--- a/src/Parser/ParserAbstract.php
+++ b/src/Parser/ParserAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Parser;
 
@@ -112,11 +114,12 @@ private function generateConnections(array $conditions): ConnectionCollectionInt
                     `?
                     \)
                 #mx',
-                    $condition,
+                    (string) $condition,
                     $matches
                 );
 
-                if (!empty($matches['childTableColumns'])
+                if (
+                    !empty($matches['childTableColumns'])
                     && !empty($matches['parentTableName'])
                     && !empty($matches['parentTableColumns'])
                 ) {
@@ -126,26 +129,22 @@ private function generateConnections(array $conditions): ConnectionCollectionInt
                             $matches['childTableColumns'][$index]
                         );
                         $childTableColumns = array_map(
-                            static function ($column): string {
-                                return trim(
-                                    $column,
-                                    '` '
-                                );
-                            },
+                            static fn(string $column): string => trim(
+                                $column,
+                                '` '
+                            ),
                             $childTableColumns
                         );
 
                         $parentTableColumns = explode(
                             ',',
-                            $matches['parentTableColumns'][$index]
+                            (string) $matches['parentTableColumns'][$index]
                         );
                         $parentTableColumns = array_map(
-                            static function ($column): string {
-                                return trim(
-                                    $column,
-                                    '` '
-                                );
-                            },
+                            static fn(string $column): string => trim(
+                                $column,
+                                '` '
+                            ),
                             $parentTableColumns
                         );
 
@@ -176,7 +175,7 @@ protected function removeLineComments($schema): string
         return preg_replace(
             '#--.+$#m',
             '',
-            $schema
+            (string) $schema
         );
     }
 
@@ -216,11 +215,13 @@ protected function removeMultiLineComments($schema): string
     protected function getSafeRandomString(string $schema): string
     {
         do {
-            $safeRandomString = (string)rand();
-        } while (strpos(
-            $schema,
-            $safeRandomString
-        ) !== false);
+            $safeRandomString = (string)random_int(0, mt_getrandmax());
+        } while (
+            str_contains(
+                $schema,
+                $safeRandomString
+            )
+        );
 
         return $safeRandomString;
     }
@@ -229,12 +230,10 @@ protected function replaceCharactersInString(string $schema, array $replacePairs
     {
         return preg_replace_callback(
             '#(\'.*\')#Uxsm',
-            static function ($matches) use ($replacePairs): string {
-                return strtr(
-                    $matches[0],
-                    $replacePairs
-                );
-            },
+            static fn($matches): string => strtr(
+                $matches[0],
+                $replacePairs
+            ),
             $schema
         );
     }
@@ -244,7 +243,7 @@ protected function removeFormating($schema): string
         return preg_replace(
             '/^\s+/m',
             '',
-            $schema
+            (string) $schema
         );
     }
 
@@ -313,7 +312,8 @@ private function parserConnections(
 
         foreach ($tables as $iteratedTable) {
             foreach ($connections as $connection) {
-                if ($connection->getChildTableName() === '*'
+                if (
+                    $connection->getChildTableName() === '*'
                     || $connection->getChildTableName() === $iteratedTable->getName()
                 ) {
                     $columns = $iteratedTable->getColumns();
@@ -321,7 +321,8 @@ private function parserConnections(
                     if (empty(array_diff($connection->getChildTableColumns(), $columns->getColumnsName()))) {
                         $parentTable = $tables->offsetGet($connection->getParentTableName());
 
-                        if ($parentTable instanceof TableInterface
+                        if (
+                            $parentTable instanceof TableInterface
                             && empty(
                                 array_diff(
                                     $connection->getParentTableColumns(),
@@ -341,7 +342,8 @@ private function parserConnections(
                                 }
                             }
 
-                            if ($iteratedTable->getPrimaryKey() instanceof PrimaryKeyInterface
+                            if (
+                                $iteratedTable->getPrimaryKey() instanceof PrimaryKeyInterface
                                 && $iteratedTable->getPrimaryKey()->getColumns() === $childTableColumns
                             ) {
                                 $oneToOne = true;
diff --git a/src/Parser/ParserInterface.php b/src/Parser/ParserInterface.php
index 00a4f2a..a95d330 100644
--- a/src/Parser/ParserInterface.php
+++ b/src/Parser/ParserInterface.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Parser;
 
diff --git a/test/Fixtures/Cassandra/FullDatabases/References/expectedSchema.php b/test/Fixtures/Cassandra/FullDatabases/References/expectedSchema.php
index 1023c9e..d92fe81 100644
--- a/test/Fixtures/Cassandra/FullDatabases/References/expectedSchema.php
+++ b/test/Fixtures/Cassandra/FullDatabases/References/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToManyConnection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
diff --git a/test/Fixtures/Mysql/FullDatabases/Auth/expectedSchema.php b/test/Fixtures/Mysql/FullDatabases/Auth/expectedSchema.php
index a67361f..5c67d3f 100644
--- a/test/Fixtures/Mysql/FullDatabases/Auth/expectedSchema.php
+++ b/test/Fixtures/Mysql/FullDatabases/Auth/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToManyConnection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
diff --git a/test/Fixtures/Mysql/FullDatabases/Auth/forcedConnection.php b/test/Fixtures/Mysql/FullDatabases/Auth/forcedConnection.php
index d9570a9..9fefc8d 100644
--- a/test/Fixtures/Mysql/FullDatabases/Auth/forcedConnection.php
+++ b/test/Fixtures/Mysql/FullDatabases/Auth/forcedConnection.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\ConnectionCollection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\NotDefinedConnection;
diff --git a/test/Fixtures/Mysql/FullDatabases/Sakila/expectedSchema.php b/test/Fixtures/Mysql/FullDatabases/Sakila/expectedSchema.php
index 9b2c1a0..bd9025b 100644
--- a/test/Fixtures/Mysql/FullDatabases/Sakila/expectedSchema.php
+++ b/test/Fixtures/Mysql/FullDatabases/Sakila/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToManyConnection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToOneConnection;
diff --git a/test/Fixtures/Mysql/FullDatabases/World/expectedSchema.php b/test/Fixtures/Mysql/FullDatabases/World/expectedSchema.php
index 43a1185..f5c5595 100644
--- a/test/Fixtures/Mysql/FullDatabases/World/expectedSchema.php
+++ b/test/Fixtures/Mysql/FullDatabases/World/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToManyConnection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/AlterTableForeignKey/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/AlterTableForeignKey/expectedSchema.php
index ea70de9..e822502 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/AlterTableForeignKey/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/AlterTableForeignKey/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Connection\OneToManyConnection;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/Comments/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/Comments/expectedSchema.php
index 8a4ecd0..6218f12 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/Comments/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/Comments/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Column;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/DifferentFormatting/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/DifferentFormatting/expectedSchema.php
index 756651f..01c1bf1 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/DifferentFormatting/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/DifferentFormatting/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Column;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/EmptyDatabase/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/EmptyDatabase/expectedSchema.php
index 4ca40d5..ffa7809 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/EmptyDatabase/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/EmptyDatabase/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Schema;
 
diff --git a/test/Fixtures/Mysql/SimpleTestCases/LowerCasedDefinitions/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/LowerCasedDefinitions/expectedSchema.php
index 631c4b0..b9b180e 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/LowerCasedDefinitions/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/LowerCasedDefinitions/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Column;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/NoPrimaryKey/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/NoPrimaryKey/expectedSchema.php
index d67dad4..5560c1f 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/NoPrimaryKey/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/NoPrimaryKey/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Column;
diff --git a/test/Fixtures/Mysql/SimpleTestCases/UpperCasedDefinitions/expectedSchema.php b/test/Fixtures/Mysql/SimpleTestCases/UpperCasedDefinitions/expectedSchema.php
index 878d36e..1e4d351 100644
--- a/test/Fixtures/Mysql/SimpleTestCases/UpperCasedDefinitions/expectedSchema.php
+++ b/test/Fixtures/Mysql/SimpleTestCases/UpperCasedDefinitions/expectedSchema.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table;
 use Pongee\DatabaseSchemaVisualization\DataObject\Sql\Database\Table\Column;
diff --git a/test/Unit/Command/Mysql/MysqlJsonCommandTest.php b/test/Unit/Command/Mysql/MysqlJsonCommandTest.php
index b7795f4..b601563 100644
--- a/test/Unit/Command/Mysql/MysqlJsonCommandTest.php
+++ b/test/Unit/Command/Mysql/MysqlJsonCommandTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Command\Mysql;
 
diff --git a/test/Unit/Command/Mysql/MysqlPlantumlCommandTest.php b/test/Unit/Command/Mysql/MysqlPlantumlCommandTest.php
index 8f31923..2e4297d 100644
--- a/test/Unit/Command/Mysql/MysqlPlantumlCommandTest.php
+++ b/test/Unit/Command/Mysql/MysqlPlantumlCommandTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Command\Mysql;
 
diff --git a/test/Unit/DataObject/Sql/Database/Connection/ConnectionAbstract.php b/test/Unit/DataObject/Sql/Database/Connection/ConnectionAbstract.php
index 79d24b0..def7f7e 100644
--- a/test/Unit/DataObject/Sql/Database/Connection/ConnectionAbstract.php
+++ b/test/Unit/DataObject/Sql/Database/Connection/ConnectionAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Connection;
 
diff --git a/test/Unit/DataObject/Sql/Database/Connection/ConnectionCollectionTest.php b/test/Unit/DataObject/Sql/Database/Connection/ConnectionCollectionTest.php
index fca34e0..a2da56a 100644
--- a/test/Unit/DataObject/Sql/Database/Connection/ConnectionCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Connection/ConnectionCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database;
 
diff --git a/test/Unit/DataObject/Sql/Database/Connection/OneToManyConnectionTest.php b/test/Unit/DataObject/Sql/Database/Connection/OneToManyConnectionTest.php
index a968106..59adfd9 100644
--- a/test/Unit/DataObject/Sql/Database/Connection/OneToManyConnectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Connection/OneToManyConnectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Connection;
 
diff --git a/test/Unit/DataObject/Sql/Database/Connection/OneToOneConnectionTest.php b/test/Unit/DataObject/Sql/Database/Connection/OneToOneConnectionTest.php
index 9bb913d..84cced2 100644
--- a/test/Unit/DataObject/Sql/Database/Connection/OneToOneConnectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Connection/OneToOneConnectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Connection;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/ColumnCollectionTest.php b/test/Unit/DataObject/Sql/Database/Table/ColumnCollectionTest.php
index 43ab03e..aed0029 100644
--- a/test/Unit/DataObject/Sql/Database/Table/ColumnCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/ColumnCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/ColumnTest.php b/test/Unit/DataObject/Sql/Database/Table/ColumnTest.php
index 81733db..d3af015 100644
--- a/test/Unit/DataObject/Sql/Database/Table/ColumnTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/ColumnTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionTest.php
index 9d5b854..ec3328b 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexTest.php
index 80d17ac..99fb2bb 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/FulltextIndexTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php b/test/Unit/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
index 9febed3..2e94630 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/NamedIndexAbstract.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/PrimaryKeyTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/PrimaryKeyTest.php
index f0b7875..0eed1f3 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/PrimaryKeyTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/PrimaryKeyTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionTest.php
index d159c88..e5b161e 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexTest.php
index 8cf1694..27c581a 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/SimpleIndexTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionTest.php
index fecb835..ac13f0b 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexTest.php
index 9674f61..e2a364a 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/SpatialIndexTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollecetionTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionTest.php
similarity index 97%
rename from test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollecetionTest.php
rename to test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionTest.php
index 1a71b80..501e787 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollecetionTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexTest.php b/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexTest.php
index 4ada378..04efdcb 100644
--- a/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexTest.php
+++ b/test/Unit/DataObject/Sql/Database/Table/Index/UniqueIndexTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database\Table\Index;
 
diff --git a/test/Unit/DataObject/Sql/Database/TableCollectionTest.php b/test/Unit/DataObject/Sql/Database/TableCollectionTest.php
index 897fe0b..58e15d6 100644
--- a/test/Unit/DataObject/Sql/Database/TableCollectionTest.php
+++ b/test/Unit/DataObject/Sql/Database/TableCollectionTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Database;
 
diff --git a/test/Unit/DataObject/Sql/Database/TableTest.php b/test/Unit/DataObject/Sql/Database/TableTest.php
index c73a8a6..7442ba9 100644
--- a/test/Unit/DataObject/Sql/Database/TableTest.php
+++ b/test/Unit/DataObject/Sql/Database/TableTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Table\Database;
 
diff --git a/test/Unit/DataObject/Sql/SchemaTest.php b/test/Unit/DataObject/Sql/SchemaTest.php
index 927ad34..ec406c8 100644
--- a/test/Unit/DataObject/Sql/SchemaTest.php
+++ b/test/Unit/DataObject/Sql/SchemaTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\DataObject\Sql\Table\Database;
 
diff --git a/test/Unit/Export/JsonTest.php b/test/Unit/Export/JsonTest.php
index a29abf4..902bf4a 100644
--- a/test/Unit/Export/JsonTest.php
+++ b/test/Unit/Export/JsonTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Export;
 
diff --git a/test/Unit/Export/PlantumlTest.php b/test/Unit/Export/PlantumlTest.php
index 3cf4c43..b0f7010 100644
--- a/test/Unit/Export/PlantumlTest.php
+++ b/test/Unit/Export/PlantumlTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Export;
 
diff --git a/test/Unit/Parser/CassandraParserTest.php b/test/Unit/Parser/CassandraParserTest.php
index d5d9c1a..b6c4c52 100644
--- a/test/Unit/Parser/CassandraParserTest.php
+++ b/test/Unit/Parser/CassandraParserTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Parser;
 
@@ -66,7 +68,7 @@ public function testParser(
         SplFileInfo $file,
         SchemaInterface $schemaObject,
         ConnectionCollectionInterface $forcedConnections
-    ) {
+    ): void {
         $sut = new CassandraParser();
         $result = $sut->run(file_get_contents($file->getRealPath()), $forcedConnections); //@todo
 
diff --git a/test/Unit/Parser/MysqlParserTest.php b/test/Unit/Parser/MysqlParserTest.php
index 1d0b389..ad54024 100644
--- a/test/Unit/Parser/MysqlParserTest.php
+++ b/test/Unit/Parser/MysqlParserTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Parser;
 
@@ -65,7 +67,7 @@ public function testParser(
         SplFileInfo $file,
         SchemaInterface $schemaObject,
         ConnectionCollectionInterface $forcedConnections
-    ) {
+    ): void {
         $sut = new MysqlParser();
         $result = $sut->run(file_get_contents($file->getRealPath()), $forcedConnections); //@todo
 
diff --git a/test/Unit/Template/Plantuml/V1TemplateTest.php b/test/Unit/Template/Plantuml/V1TemplateTest.php
index fac9ddb..1649020 100644
--- a/test/Unit/Template/Plantuml/V1TemplateTest.php
+++ b/test/Unit/Template/Plantuml/V1TemplateTest.php
@@ -1,4 +1,6 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 namespace Pongee\DatabaseSchemaVisualization\Test\Unit\Tempalte\Plantuml;
 
@@ -371,7 +373,7 @@ public function getSchemaProvider(): array
     /**
      * @dataProvider getSchemaProvider
      */
-    public function testExport(SchemaInterface $schema, string $extendOutput)
+    public function testExport(SchemaInterface $schema, string $extendOutput): void
     {
         $template = file_get_contents(__DIR__ . '/../../../../src/Template/Plantuml/v1.twig');
 
@@ -386,10 +388,10 @@ public function testExport(SchemaInterface $schema, string $extendOutput)
     protected function trim($text): string
     {
         return trim(
-            preg_replace(
+            (string) preg_replace(
                 '/^\s+/m',
                 '',
-                $text
+                (string) $text
             )
         );
     }
diff --git a/test/bootstrap.php b/test/bootstrap.php
index 2d0e99e..f3bb0aa 100644
--- a/test/bootstrap.php
+++ b/test/bootstrap.php
@@ -1,3 +1,5 @@
-<?php declare(strict_types=1);
+<?php
+
+declare(strict_types=1);
 
 define('FIXTURES_DIRECTORY', __DIR__ . '/Fixtures/');