match url pattern in php using regular expression

Question

I want to match a url link in wall post and replace this link with anchor tag, for this I use the regular expression below.

I would like the match 4 types of url:

1. http://example.com
2. https://example.com
3. www.example.com
4. example.com

preg_replace('@(https?://([-\w\.]+)+(:\d+)?(/([\w/_\.]*(\?\S+)?)?)?)@',
             '<a href="$1">$1</a>', $subject);

This expression matches only first two types of url.

If I use this expression for match url pattern '@(www?([-\w\.]+)+(:\d+)?(/([\w/_\.]*(\?\S+)?)?)?)@', then it only matches the third type of url pattern.

How can I match all four type of url pattern with a single regular expression?

Answer 1

I'd use a different regex to be honest. Like this one that Gruber posted last year

http://daringfireball.net/2009/11/liberal_regex_for_matching_urls

Answer 2

If you want to make that one work you need to make the "https?//" part optional, since you seem to have a fairly good grasp of regexps I won't show you, an excerise for the reader :)

But I generally agree with Nev, it's overly complicated for what it does.