regular expressions and Phone validation

Hi all, I have one small problem I don't understand the preg_replace() method. I understand the gist of what it does but I still don't fully know what it does. I have read the entry in the php manual about this and I am still confused about it. I've never been any good with regular expressions. Here is the function in use: function checkPhone ($Phone) { global $errmsg; if (!empty($Phone)) { $Phone = ereg_replace("[^0-9]", '', $Phone); if ((strlen($Phone)) <= 14) return preg_replace("/[^0-9]*([0-9]{3})[^0-9]*([0-9]{3})[^0-9]*([0-9]{4}).*/", "(\\1) \\2-\\3",$Phone); } } I think my problem is mostly what is returned when preg_replace executes? Paul