Regex code to replace url at link

[haimz]

Hello evryone
i need aregex code that replacing
url: http://domain.com at
link: <a href="http://domain.com" rel="nofollow">http://domain.com</a>

replace the url until space

[twiss]

There's a nice one there: http://daringfireball.net/2010/07/improved_regex_for_matching_urls

$url = "http://www.diafol.org";
echo preg_replace("/(http:\/\/\S+)\s*/","<a href=\"$1\" rel=\"nofollow\">$1</a>",$url);

that'll work on the simplest of urls. check out url matches, e.g. ftp, https, with querystrings and username/pw and anchor hashes etc