Why is the php parser not working?

Question

PHP

The script seems to be correct but gives a 500 error

<?php
$result = "<source src="http://site.com/592caa503725b373?download_token=e142c54f24af82854fa39cac8c0c8838826caef5dd12ef5a97314ec818399f20" type="video/mp4">";
preg_match_all("/(?<=download_token=).*(?=" type="video\/mp4/"), $result, $video );
var_dump($video);
?>

Answer 1

You messed up with double and single quotes, your ide doesn't highlight it?