diff --git a/src/wp-includes/template.php b/src/wp-includes/template.php
index f799113e9c26e..f17307e19daa2 100644
--- a/src/wp-includes/template.php
+++ b/src/wp-includes/template.php
@@ -926,13 +926,24 @@ function wp_finalize_template_enhancement_output_buffer( string $output, int $ph
$is_html_content_type = null;
$html_content_types = array( 'text/html', 'application/xhtml+xml' );
foreach ( headers_list() as $header ) {
- $header_parts = preg_split( '/\s*[:;]\s*/', strtolower( $header ) );
+ $header_parts = explode( ':', strtolower( $header ), 2 );
if (
- is_array( $header_parts ) &&
- count( $header_parts ) >= 2 &&
+ count( $header_parts ) === 2 &&
'content-type' === $header_parts[0]
) {
- $is_html_content_type = in_array( $header_parts[1], $html_content_types, true );
+ /*
+ * This is looking for very specific content types, therefore it
+ * doesn’t need to fully parse the header’s value. Instead, it needs
+ * only assert that the content type is one of the static HTML types.
+ *
+ * Example:
+ *
+ * Content-Type: text/html; charset=utf8
+ * Content-Type: text/html ;charset=latin4
+ * Content-Type:application/xhtml+xml
+ */
+ $media_type = trim( strtok( $header_parts[1], ';' ), " \t" );
+ $is_html_content_type = in_array( $media_type, $html_content_types, true );
break; // PHP only sends the first Content-Type header in the list.
}
}
diff --git a/tests/phpunit/tests/template.php b/tests/phpunit/tests/template.php
index f7dcf015bff03..89136c00e3361 100644
--- a/tests/phpunit/tests/template.php
+++ b/tests/phpunit/tests/template.php
@@ -597,6 +597,9 @@ static function ( string $buffer ) use ( &$filter_args ): string {
PHP_INT_MAX
);
+ $this->assertCount( 0, headers_list(), 'Expected no headers to have been sent during unit tests.' );
+ ini_set( 'default_mimetype', 'text/html' ); // Since sending a header won't work.
+
$initial_ob_level = ob_get_level();
$this->assertTrue( wp_start_template_enhancement_output_buffer(), 'Expected wp_start_template_enhancement_output_buffer() to return true indicating the output buffer started.' );
$this->assertSame( 1, did_action( 'wp_template_enhancement_output_buffer_started' ), 'Expected the wp_template_enhancement_output_buffer_started action to have fired.' );
@@ -676,6 +679,9 @@ static function ( string $buffer ) use ( &$applied_filter ): string {
}
);
+ $this->assertCount( 0, headers_list(), 'Expected no headers to have been sent during unit tests.' );
+ ini_set( 'default_mimetype', 'text/html' ); // Since sending a header won't work.
+
$initial_ob_level = ob_get_level();
$this->assertTrue( wp_start_template_enhancement_output_buffer(), 'Expected wp_start_template_enhancement_output_buffer() to return true indicating the output buffer started.' );
$this->assertSame( 1, did_action( 'wp_template_enhancement_output_buffer_started' ), 'Expected the wp_template_enhancement_output_buffer_started action to have fired.' );
@@ -740,6 +746,9 @@ static function ( string $buffer ) use ( &$called_filter ): string {
}
);
+ $this->assertCount( 0, headers_list(), 'Expected no headers to have been sent during unit tests.' );
+ ini_set( 'default_mimetype', 'application/xhtml+xml' ); // Since sending a header won't work.
+
$initial_ob_level = ob_get_level();
$this->assertTrue( wp_start_template_enhancement_output_buffer(), 'Expected wp_start_template_enhancement_output_buffer() to return true indicating the output buffer started.' );
$this->assertSame( 1, did_action( 'wp_template_enhancement_output_buffer_started' ), 'Expected the wp_template_enhancement_output_buffer_started action to have fired.' );
@@ -749,15 +758,18 @@ static function ( string $buffer ) use ( &$called_filter ): string {
+
Unprocessed
Hello World!
+ '; ?>
-
+
+
Template Replaced
@@ -799,7 +811,9 @@ public function test_wp_start_template_enhancement_output_buffer_for_json(): voi
$this->assertSame( 1, did_action( 'wp_template_enhancement_output_buffer_started' ), 'Expected the wp_template_enhancement_output_buffer_started action to have fired.' );
$this->assertSame( $initial_ob_level + 1, ob_get_level(), 'Expected the output buffer level to have been incremented.' );
+ $this->assertCount( 0, headers_list(), 'Expected no headers to have been sent during unit tests.' );
ini_set( 'default_mimetype', 'application/json' ); // Since sending a header won't work.
+
$json = wp_json_encode(
array(
'success' => true,