The code changes in `RequestMixin.php` fix the array merging functionality by using `array_replace` instead of `array_merge`. This ensures that the merged array contains the values from both arrays, with the values from the second array overwriting the values from the first array. The change also includes a `@phpstan-ignore-line` comment to suppress a PHPStan error.
Note: This message has been generated based on the provided code changes and recent commits.