Hyperlink filtering from a body of text (with hack to catch t.co links because I don't like RegEx at all).

filter_hyperlink.php

	/**
	 * Auto convert hyperlinks in text
	 *
	 * @param   string  Text to filter
	 * @return  string  Filtered text
	 * @url     http://www.php.net/manual/en/function.preg-replace.php#77787
	 */
	function filter_hyperlink($text) {
	    $text=preg_replace("/(http:\/\/|www|[a-zA-Z0-9-]+\.|[a-zA-Z0-9\.-]+@)(([a-zA-Z0-9-][a-zA-Z0-9-]+\.)+[a-zA-Z0-9-\.\/\_\?\%\#\&\=\;\~\!\(\)]+)/","<a href=\"http://\\1\\2\">\\1\\2</a>",$text);
	    $text=preg_replace("/(http:\/\/t\.co\/[a-zA-Z0-9-\.\/\_\?\%\#\&\=\;\~\!\(\)]+)/","<a href=\"http://\\1\\2\">\\1\\2</a>",$text); // Hack for twitter t.co links

	    // Remove double protocols
	    $text = str_replace('<a href="http://http://', '<a href="http://', $text);

	    return $text;
	}