<?php

$remove_from_beginning = array( 'www.', 'wap.', 'admin.' );
$final = "";

foreach( $remove_from_beginning as $start )
{
	$final = $final . "" . substr_replace($start, '', -1) . "" . "\.|";
}

$final = substr_replace($final, '', -1);

echo preg_replace("/" . "" . "(?:" . "" . $final . "" . ")" . "" . "(.*)" . "" . "/", "$1", "www.wap.com");