Mine

function formatURL($text) {
	$normal= '/^http?:\/\/[a-z0-9-]+(\.[a-z0-9-]+)+/i';
	$secure= '/^https:\/\/[a-z0-9-]+(\.[a-z0-9-]+)+/i';
	if (preg_match($secure, $text)):
			return $text;
	else:
		if (preg_match($normal, $text)):
			return $text;
		else:
			return "http://".$text;		
		endif;	
	endif;
}