Which regexp php is using for filter_var($url, FILTER_VALIDATE_URL)?

filter_var($url, FILTER_VALIDATE_URL) seems to be great way to detect if $url contains url or not. Is there any way to see what regular expression this function uses for detecting?

Thank you

Answer

It uses something else then a regex. In C, it checks the return of the php_url_parse_ex()(C) function, which you can see at: ext/standard/url.c, line 97, called at ext/filter/logical_filters.c, line 440.

In these terms: if you call parse_url()(PHP) in PHP, and perform the same checks as in php_filter_validate_url()(C), you’d have the same output.