Fix infinite recursion in category tree traversal

phpmyfaq/src/phpMyFAQ/Category/Order.php

@@ -120,15 +120,33 @@ public function setCategoryTree(
      * Returns the category tree.
      *
      * @param stdClass[] $categories
+     * @param int $parentId
+     * @param array $visited Track visited categories to prevent infinite recursion
      */
-    public function getCategoryTree(array $categories, int $parentId = 0): array
+    public function getCategoryTree(array $categories, int $parentId = 0, array &$visited = []): array
     {
         $result = [];
 
         foreach ($categories as $category) {
-            if ((int)$category['parent_id'] === $parentId) {
-                $childCategories = $this->getCategoryTree($categories, (int)$category['category_id']);
-                $result[$category['category_id']] = $childCategories;
+            $categoryId = (int)$category['category_id'];
+            $categoryParentId = (int)$category['parent_id'];
+
+            // Skip if category is its own parent or creates a cycle
+            if ($categoryId === $categoryParentId) {
+                continue;
+            }
+
+            if ($categoryParentId === $parentId) {
+                // Check if this category has already been visited to prevent cycles
+                if (isset($visited[$categoryId])) {
+                    continue;
+                }
+
+                // Add current category to visited list
+                $visited[$categoryId] = true;
+
+                $childCategories = $this->getCategoryTree($categories, $categoryId, $visited);
+                $result[$categoryId] = $childCategories;
             }
         }
 

tests/phpMyFAQ/Category/OrderTest.php

@@ -129,4 +129,78 @@ public function testGetParentId(): void
 
         $this->assertEquals($expected, $actual);
     }
+
+    /**
+     * Test that getCategoryTree handles self-referencing categories without infinite recursion
+     */
+    public function testGetCategoryTreeWithSelfReference(): void
+    {
+        // Simulate a category that references itself as parent
+        $categories = [
+            [
+                'category_id' => 1,
+                'parent_id' => 1, // Self-reference
+                'position' => 1,
+            ],
+            [
+                'category_id' => 2,
+                'parent_id' => 0,
+                'position' => 2,
+            ],
+        ];
+
+        $result = $this->categoryOrder->getCategoryTree($categories);
+
+        // Category 1 should be skipped due to self-reference
+        // Only category 2 should be in the result
+        $expected = [
+            2 => [],
+        ];
+
+        $this->assertEquals($expected, $result);
+    }
+
+    /**
+     * Test that getCategoryTree handles circular references without infinite recursion
+     */
+    public function testGetCategoryTreeWithCircularReference(): void
+    {
+        // Simulate circular reference: 1 -> 2 -> 3 -> 2 (cycle)
+        $categories = [
+            [
+                'category_id' => 1,
+                'parent_id' => 0,
+                'position' => 1,
+            ],
+            [
+                'category_id' => 2,
+                'parent_id' => 1,
+                'position' => 2,
+            ],
+            [
+                'category_id' => 3,
+                'parent_id' => 2,
+                'position' => 3,
+            ],
+            [
+                'category_id' => 2, // Duplicate entry creating circular reference
+                'parent_id' => 3,
+                'position' => 4,
+            ],
+        ];
+
+        $result = $this->categoryOrder->getCategoryTree($categories);
+
+        // Should handle circular reference gracefully
+        // Category 2 should only be visited once
+        $expected = [
+            1 => [
+                2 => [
+                    3 => [],
+                ],
+            ],
+        ];
+
+        $this->assertEquals($expected, $result);
+    }
 }