silly regex

<?php
if($body = stripslashes($_POST['body'])){
    $pattern[0] = '#(http:\/\/)?(www.)?(youtube\.com\/watch\?v[=]([a-zA-Z0-9]+))#';
    $pattern[1] = '#(http:\/\/)?(www.)?[0-9a-zA-Z]+\.[a-zA-Z]+(\/[0-9a-zA-Z]*\?(&*\w+[=](\w+))*)?#';
    $replacement[0] = '<iframe width="560" height="315" src="http://www.youtube.com/embed/$4" frameborder="0" allowfullscreen></iframe>';
    $replacement[1] = "<a href=\"$&\" target=\"_blank\">$&</a>";
    $body = preg_replace($pattern, $replacement, $body);
    echo $body;
}