- var_dump: documentation ( source)
- preg_match: documentation ( source)
<?php
preg_match('/^((?:(?:[^?+*{}()[\\]\\\\|]+|\\\\.|\\[(?:\\^?\\\\.|\\^[^\\\\]|[^\\\\^])(?:[^\\]\\\\]+|\\\\.)*\\]|\\((?:\\?[:=!]|\\?<[=!]|\\?>)?(?1)??\\)|\\(\\?(?:R|[+-]?\\d+)\\))(?:(?:[?+*]|\\{\\d+(?:,\\d*)?\\})[?+]?)?|\\|)*)$/', '~1~', $matches);
var_dump($matches);