diff --git a/includes/Checker/Checks/General/Php_Error_Reporting_Check.php b/includes/Checker/Checks/General/Php_Error_Reporting_Check.php
new file mode 100644
index 000000000..1748ee54a
--- /dev/null
+++ b/includes/Checker/Checks/General/Php_Error_Reporting_Check.php
@@ -0,0 +1,267 @@
+<?php
+/**
+ * Class Php_Error_Reporting_Check.
+ *
+ * @package plugin-check
+ */
+
+namespace WordPress\Plugin_Check\Checker\Checks\General;
+
+use PhpParser\Error;
+use PhpParser\Node;
+use PhpParser\Node\Expr;
+use PhpParser\Node\Stmt;
+use PhpParser\NodeFinder;
+use PhpParser\ParserFactory;
+use WordPress\Plugin_Check\Checker\Check_Categories;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\Abstract_File_Check;
+use WordPress\Plugin_Check\Traits\Amend_Check_Result;
+use WordPress\Plugin_Check\Traits\Stable_Check;
+
+/**
+ * Check for production-time PHP error reporting changes.
+ *
+ * @since 1.9.0
+ */
+class Php_Error_Reporting_Check extends Abstract_File_Check {
+
+	use Amend_Check_Result;
+	use Stable_Check;
+
+	/**
+	 * Gets the categories for the check.
+	 *
+	 * Every check must have at least one category.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @return array The categories for the check.
+	 */
+	public function get_categories() {
+		return array(
+			Check_Categories::CATEGORY_GENERAL,
+		);
+	}
+
+	/**
+	 * Amends the given result by running the check on the given list of files.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @param Check_Result $result The check result to amend, including the plugin context to check.
+	 * @param array        $files  List of absolute file paths.
+	 */
+	protected function check_files( Check_Result $result, array $files ) {
+		$php_files   = self::filter_files_by_extension( $files, 'php' );
+		$plugin_path = $result->plugin()->path();
+
+		foreach ( $php_files as $file ) {
+			// Skip test suite folders or files relative to the plugin's root path.
+			$relative_file = str_replace( $plugin_path, '', $file );
+			if ( preg_match( '#^(?:tests|test|testdata|phpunit)/#i', $relative_file ) || preg_match( '#/phpunit[^/]*$#i', $relative_file ) ) {
+				continue;
+			}
+
+			$this->check_file( $result, $file );
+		}
+	}
+
+	/**
+	 * Scans a single PHP file for error reporting violations.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @param Check_Result $result The check result to amend.
+	 * @param string       $file   Absolute path to the file.
+	 */
+	private function check_file( Check_Result $result, string $file ) {
+		$contents = file_get_contents( $file );
+		if ( false === $contents ) {
+			return;
+		}
+
+		// Try AST-based detection first.
+		$parser = ( new ParserFactory() )->create( ParserFactory::PREFER_PHP7 );
+		try {
+			$ast = $parser->parse( $contents );
+			if ( null !== $ast ) {
+				$this->check_ast( $result, $file, $ast );
+				return;
+			}
+		} catch ( Error $e ) {
+			// Fall through to regex-based detection if parsing fails.
+		}
+
+		$this->check_regex( $result, $file, $contents );
+	}
+
+	/**
+	 * Scans the AST of a file for error reporting violations.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @param Check_Result $result The check result to amend.
+	 * @param string       $file   Absolute path to the file.
+	 * @param array        $ast    The parsed AST nodes.
+	 *
+	 * @SuppressWarnings(PHPMD.NPathComplexity)
+	 */
+	private function check_ast( Check_Result $result, string $file, array $ast ) {
+		$node_finder = new NodeFinder();
+		$func_calls  = $node_finder->findInstanceOf( $ast, Expr\FuncCall::class );
+
+		foreach ( $func_calls as $func_call ) {
+			// @phpstan-ignore-next-line Access to property $name on Expr\FuncCall.
+			if ( ! $func_call->name instanceof Node\Name ) {
+				continue;
+			}
+
+			// @phpstan-ignore-next-line Access to property $name on Expr\FuncCall.
+			$func_name = strtolower( $func_call->name->toString() );
+			$line      = method_exists( $func_call, 'getStartLine' ) ? $func_call->getStartLine() : 0;
+
+			// 1. Direct calls to error_reporting().
+			if ( 'error_reporting' === $func_name ) {
+				$this->add_violation( $result, $file, $line );
+				continue;
+			}
+
+			// 2. ini_set() / ini_alter().
+			if ( in_array( $func_name, array( 'ini_set', 'ini_alter' ), true ) ) {
+				if ( ! empty( $func_call->args[0] ) ) {
+					$first_arg = $func_call->args[0]->value;
+					if ( $first_arg instanceof Node\Scalar\String_ ) {
+						$arg_value = strtolower( $first_arg->value );
+						if ( in_array( $arg_value, array( 'error_reporting', 'display_errors' ), true ) ) {
+							$this->add_violation( $result, $file, $line );
+							continue;
+						}
+					}
+				}
+			}
+
+			// 3. define() overrides.
+			if ( 'define' === $func_name ) {
+				if ( ! empty( $func_call->args[0] ) ) {
+					$first_arg = $func_call->args[0]->value;
+					if ( $first_arg instanceof Node\Scalar\String_ ) {
+						$arg_value = $first_arg->value;
+						if ( in_array( $arg_value, array( 'WP_DEBUG', 'WP_DEBUG_LOG', 'WP_DEBUG_DISPLAY', 'SCRIPT_DEBUG' ), true ) ) {
+							$this->add_violation( $result, $file, $line );
+							continue;
+						}
+					}
+				}
+			}
+		}
+
+		// Also check for the const keyword: e.g. const WP_DEBUG = true.
+		$consts = $node_finder->findInstanceOf( $ast, Stmt\Const_::class );
+		foreach ( $consts as $const_stmt ) {
+			// @phpstan-ignore-next-line Access to property $consts on Stmt\Const_.
+			foreach ( $const_stmt->consts as $const ) {
+				$const_name = $const->name->toString();
+				$line       = method_exists( $const, 'getStartLine' ) ? $const->getStartLine() : 0;
+				if ( in_array( $const_name, array( 'WP_DEBUG', 'WP_DEBUG_LOG', 'WP_DEBUG_DISPLAY', 'SCRIPT_DEBUG' ), true ) ) {
+					$this->add_violation( $result, $file, $line );
+				}
+			}
+		}
+	}
+
+	/**
+	 * Fallback regex-based detection for error reporting violations.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @param Check_Result $result   The check result to amend.
+	 * @param string       $file     Absolute path to the file.
+	 * @param string       $contents File contents.
+	 */
+	private function check_regex( Check_Result $result, string $file, string $contents ) {
+		// Clean comments before checking regex.
+		$cleaned = preg_replace( '/\/\*.*?\*\//s', '', $contents );
+		$cleaned = preg_replace( '/\/\/.*$/m', '', $cleaned );
+		$cleaned = preg_replace( '/#.*$/m', '', $cleaned );
+
+		$patterns = array(
+			// error_reporting(...).
+			'/\berror_reporting\s*\(/i',
+			// ini_set(...) / ini_alter(...).
+			'/\bini_(?:set|alter)\s*\(\s*[\'"](?:error_reporting|display_errors)[\'"]/i',
+			// define(...).
+			'/\bdefine\s*\(\s*[\'"](?:WP_DEBUG|WP_DEBUG_LOG|WP_DEBUG_DISPLAY|SCRIPT_DEBUG)[\'"]/i',
+			// const WP_DEBUG = ....
+			'/\bconst\s+(?:WP_DEBUG|WP_DEBUG_LOG|WP_DEBUG_DISPLAY|SCRIPT_DEBUG)\b/i',
+		);
+
+		// Scan line by line to locate line numbers.
+		$lines = explode( "\n", $cleaned );
+		foreach ( $lines as $index => $line_content ) {
+			$line_num = $index + 1;
+			foreach ( $patterns as $pattern ) {
+				if ( preg_match( $pattern, $line_content ) ) {
+					$this->add_violation( $result, $file, $line_num );
+					break; // Only flag once per line.
+				}
+			}
+		}
+	}
+
+	/**
+	 * Adds a standard warning message for a violation.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @param Check_Result $result The check result to amend.
+	 * @param string       $file   Absolute path to the file.
+	 * @param int          $line   The line number on which the warning occurred.
+	 */
+	private function add_violation( Check_Result $result, string $file, int $line ) {
+		$message = sprintf(
+			'<strong>%1$s</strong><br><br>%2$s<br><br>%3$s<br><br>%4$s',
+			__( 'Do not change PHP error reporting in production code', 'plugin-check' ),
+			__( 'A plugin should not modify PHP\'s error-reporting configuration. Calls such as <code>error_reporting()</code>, <code>ini_set(\'display_errors\', &hellip;)</code>, or redefining <code>WP_DEBUG</code>, <code>WP_DEBUG_LOG</code>, <code>WP_DEBUG_DISPLAY</code> or <code>SCRIPT_DEBUG</code> change behaviour for every other plugin and theme on the site.', 'plugin-check' ),
+			__( 'This can leak sensitive information (paths, secrets, stack traces) and breaks the standard debugging workflow for site owners and other developers. The host\'s <code>php.ini</code> and the site\'s <code>wp-config.php</code> are the correct places to control this.', 'plugin-check' ),
+			__( 'Please remove these calls, or move them behind a strictly developer-only flag that is never set in shipped code.', 'plugin-check' )
+		);
+
+		$this->add_result_warning_for_file(
+			$result,
+			$message,
+			'php_error_reporting_detected',
+			$file,
+			$line,
+			0,
+			'https://www.php.net/manual/en/function.error-reporting.php',
+			8
+		);
+	}
+
+	/**
+	 * Gets the description for the check.
+	 *
+	 * Every check must have a short description explaining what the check does.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @return string Description.
+	 */
+	public function get_description(): string {
+		return __( 'Detects runtime changes to PHP error reporting configuration or WordPress debug constants.', 'plugin-check' );
+	}
+
+	/**
+	 * Gets the documentation URL for the check.
+	 *
+	 * Every check must have a URL with further information about the check.
+	 *
+	 * @since 1.9.0
+	 *
+	 * @return string The documentation URL.
+	 */
+	public function get_documentation_url(): string {
+		return 'https://www.php.net/manual/en/function.error-reporting.php';
+	}
+}
diff --git a/includes/Checker/Default_Check_Repository.php b/includes/Checker/Default_Check_Repository.php
index c22371044..f6ada18c0 100644
--- a/includes/Checker/Default_Check_Repository.php
+++ b/includes/Checker/Default_Check_Repository.php
@@ -72,6 +72,7 @@ private function register_default_checks() {
 			'wp_plugin_check_checks',
 			array(
 				'i18n_usage'                 => new Checks\General\I18n_Usage_Check(),
+				'php_error_reporting'        => new Checks\General\Php_Error_Reporting_Check(),
 				'enqueued_scripts_size'      => new Checks\Performance\Enqueued_Scripts_Size_Check(),
 				'enqueued_styles_size'       => new Checks\Performance\Enqueued_Styles_Size_Check(),
 				'code_obfuscation'           => new Checks\Plugin_Repo\Code_Obfuscation_Check(),
diff --git a/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-with-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-with-errors/load.php
new file mode 100644
index 000000000..c776b4c1e
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-with-errors/load.php
@@ -0,0 +1,26 @@
+<?php
+/**
+ * Plugin Name: Test Plugin - PHP Error Reporting With Errors
+ * Description: Test plugin that triggers warnings for changing PHP error reporting settings.
+ * Version: 1.0.0
+ * Author: WordPress.org
+ * Text Domain: test-plugin-php-error-reporting-with-errors
+ *
+ * @package plugin-check
+ */
+
+error_reporting( 0 );
+
+error_reporting( E_ALL );
+
+ini_set( 'display_errors', 1 );
+
+ini_set( 'error_reporting', E_ALL );
+
+ini_alter( 'display_errors', 0 );
+
+define( 'WP_DEBUG', true );
+
+define( 'WP_DEBUG_LOG', true );
+
+define( 'SCRIPT_DEBUG', true );
diff --git a/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/load.php b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/load.php
new file mode 100644
index 000000000..ac7b4ba5c
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/load.php
@@ -0,0 +1,16 @@
+<?php
+/**
+ * Plugin Name: Test Plugin - PHP Error Reporting Without Errors
+ * Description: Test plugin that does not trigger warnings for changing PHP error reporting settings.
+ * Version: 1.0.0
+ * Author: WordPress.org
+ * Text Domain: test-plugin-php-error-reporting-without-errors
+ *
+ * @package plugin-check
+ */
+
+// Memory limit changes are allowed.
+ini_set( 'memory_limit', '256M' );
+
+// Unaffected define statements are allowed.
+define( 'MY_CUSTOM_CONSTANT', true );
diff --git a/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/tests/some-test.php b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/tests/some-test.php
new file mode 100644
index 000000000..b10ebc812
--- /dev/null
+++ b/tests/phpunit/testdata/plugins/test-plugin-php-error-reporting-without-errors/tests/some-test.php
@@ -0,0 +1,14 @@
+<?php
+/**
+ * PHPUnit test case containing error reporting configurations.
+ *
+ * @package plugin-check
+ */
+
+class Some_Test_Case {
+	public function test_something() {
+		error_reporting( 0 );
+		ini_set( 'display_errors', 1 );
+		define( 'WP_DEBUG', true );
+	}
+}
diff --git a/tests/phpunit/tests/Checker/Checks/Php_Error_Reporting_Check_Tests.php b/tests/phpunit/tests/Checker/Checks/Php_Error_Reporting_Check_Tests.php
new file mode 100644
index 000000000..e59c5b448
--- /dev/null
+++ b/tests/phpunit/tests/Checker/Checks/Php_Error_Reporting_Check_Tests.php
@@ -0,0 +1,40 @@
+<?php
+
+use WordPress\Plugin_Check\Checker\Check_Context;
+use WordPress\Plugin_Check\Checker\Check_Result;
+use WordPress\Plugin_Check\Checker\Checks\General\Php_Error_Reporting_Check;
+
+class Php_Error_Reporting_Check_Tests extends WP_UnitTestCase {
+
+	public function test_run_with_errors() {
+		$check        = new Php_Error_Reporting_Check();
+		$context      = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-php-error-reporting-with-errors/load.php' );
+		$check_result = new Check_Result( $context );
+
+		$check->run( $check_result );
+
+		$warnings = $check_result->get_warnings();
+
+		$this->assertNotEmpty( $warnings );
+		$this->assertArrayHasKey( 'load.php', $warnings );
+
+		$this->assertEquals( 8, $check_result->get_warning_count() );
+
+		$first_line_warnings   = reset( $warnings['load.php'] );
+		$first_column_warnings = reset( $first_line_warnings );
+		$warning_data          = reset( $first_column_warnings );
+
+		$this->assertEquals( 'php_error_reporting_detected', $warning_data['code'] );
+	}
+
+	public function test_run_without_errors() {
+		$check        = new Php_Error_Reporting_Check();
+		$context      = new Check_Context( UNIT_TESTS_PLUGIN_DIR . 'test-plugin-php-error-reporting-without-errors/load.php' );
+		$check_result = new Check_Result( $context );
+
+		$check->run( $check_result );
+
+		$this->assertEquals( 0, $check_result->get_warning_count() );
+		$this->assertEquals( 0, $check_result->get_error_count() );
+	}
+}