What is the RFC compliant and working regular expression to check if a string is a valid URL

Question

There is question by the almost the same name already: What is the best regular expression to check if a string is a valid URL

I don\'t understand this stackoverflow

Answer 1

Thanks ircmaxell but I had to adjust a little the IPV6 regex for PHP to compile with preg_match.

I changed:

$ipv6 = "([({$rawIpv6}|{$ipv4sub})])";

To :

$ipv6 = "({$rawIpv6}|{$ipv4sub})";