Regex Help (URL to Link)

[big_nerd]

I am attempting to do a URL to Link algorithm, however I need it to add target="_blank" at the end of the link, BUT I would also like it to be smart, as there are some where they will make their own links, but i want it so the ones that arent are done automatically, but ignoring the other links..

I have this so far:

function url2l($url) {
	if (preg_match("/^http:/i", $url)) {
			$str = ereg_replace("[[:alpha:]]+://[^<>[:space:]]+[[:alnum:]/]","<a href=\"\\0\" target=\"_blank\">\\0</a>", $str);
	} else {
		echo "no";
	}
	return $str;
}

in theory it is supposed to look for http: in the beginning of a word.

Of course there are a multitude of issues with this (beyond it not working).

So any help would be apreciated. I can NEVER get this regex stuff.

edit::

I have done this (which seems to be working) but I am looking forward to any better ways...

function url2link($blank) {
	if (!preg_match("/^<a href/i",$blank)) {
		$blank = preg_replace( "/(?<!<a href=\")((http|ftp)+(s)?:\/\/[^<>\s]+)/i", "<a href=\"\\0\">$blank</a>", $blank );
	}
	return $blank;
}

Regards,