正则表达式正则表达式匹配大多数URL需要改进

Question

I need a function which will check for the existing URLs in a string.

function linkcleaner($url) {
$regex="(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:'".,<>?«»“”‘’]))";

if(preg_match($regex, $url, $matches)) {
echo $matches[0];
}
}

The regular expression is taken from the John Gruber's blog, where he addressed the problem of creating a regex matching all the URLs. Unfortunately, I can't make it work. It seems the problem is coming from the double quotes inside the regex or the other punct symbols at the end of the expression. Any help is appreciated. Thank you!

Answer 1

Apart from @tandu's answer, you also need delimiters for a regex in php.

The easiest would be to start and end your pattern with an # as that character does not appear in it:

$regex="#(?i)\b((?:[a-z][\w-]+:(?:/{1,3}|[a-z0-9%])|www\d{0,3}[.]|[a-z0-9.\-]+[.][a-z]{2,4}/)(?:[^\s()<>]+|\(([^\s()<>]+|(\([^\s()<>]+\)))*\))+(?:\(([^\s()<>]+|(\([^\s()<>]+\)))*\)|[^\s`!()\[\]{};:\'\".,<>?«»“”‘’]))#";