DOMXPath缓慢解析网址？

I'm trying to parse several url's just to see if a certain div id exists. First I tried using simplehtmldom but it was very slow, so the latest I've tried is domxpath. It still takes roughly the same amount of time for the page to load. I'm pretty new to all this so I don't know what kind of limitations there are to parsing. You will notice in my code I'm using unset to try and clear the memory after it loops through each time. It didn't make any difference on performance but I just left it in because it wasn't affecting anything, and I'm not sure if it's necessary to have that in there or not?

So..my question is, from taking a look at my code below, is there anything I could do to parse these url's any faster? Also, is parsing 50 url's for what I'm wanting to do too much to ask? Thank you in advance.

<?php
    require_once("include.all.php");
    if ( !class_exists( "Standings" ) ) {
        Class Standings {
            public static function Status( $url ) {
                $html = file_get_contents($url);        
                $doc = new DOMDocument;
                $previous_value = libxml_use_internal_errors(TRUE);
                $doc->Loadhtml($html);
                libxml_clear_errors();
                libxml_use_internal_errors($previous_value);
                $element = $doc->getElementById( 'cams_view_top' );
                if ( $element == null ) {
                    echo "<img src='images/offline.fw.png'/>";
                    unset( $doc,$html );
                } else {
                    echo "<img src='images/online.fw.png'/>"; 
                    unset( $doc,$html );
                }
            }
        }
    }
?>