As i wanted loads of URLs to test some SVG validating experiments on i set out to write a spider. Somehow the HttpRequest didn't get installed right, so i messed up my code a bit more, making it way less efficient along the way, by using web-sniffer. That didn't work right away, i lost energy, and now i put it here so i (or better, someone else) can find it and improve it later.

<?php
header("Content-Type:text/plain");

$link=array();
$link['uri']="http://svg.startpagina.nl";
$link['level']=0;

$low=0;
$high=$low;

$links=array();
$links[$low]=$link;

$deepest=3;
while(true){
    search($links[$low++]);
}

function extension($url){ // svg html
    $path_parts = pathinfo(parse_url($url,PHP_URL_PATH));
    return $path_parts['extension'];
}

function hPos($end){
    return (stripos($content,"href=",$end));
}

function addLinks($content,$level){
    global $links,$deepest,$high;
    $end=1;
    if($level<$deepest){
        for($start=hPos($end); $start>0; $start=hPos($end)){
            $opensq=strpos($content,"'",$start);
            $opendq=strpos($content,'"',$start);
            if ($opensq<$opendq) {
                $quot="'";
            }else{
                $quot='"';
            }
            $start=min($opensq,$opendq)+1;
            $end=strpos($content,$quot,$start)-1;
            $extra=array();
            $extra['uri']=substr($content,$start,$end-$start+1);
            $extra['level']=$level+1;
            $links[++$high]=$extra;
        }
    }
}

function search($link){
    global $links,$deepest;
    print_r($links);
    $uri=$link['uri'];
if ($uri!=""){   
    $level=$link['level'];
    if ($level>$deepest) {exit();}
    if ($level==0) {
        $ext="html";
    }else{
        $ext=extension($uri);
    }
    if ($ext=="svg") { echo "\n".$uri ; }
    //$req = new HttpRequest($uri, HttpRequest::METH_GET);  // Parse error: parse error, expecting `'('' in c:\program files\easyphp1-8\www\megavalidate.php on line 62
    //try{
/*
        $req->send();
       if ($req->getResponseCode() == 200) {
           $mime=$req->getResponseHeader("Content-Type");
*/
            sleep(10);
            $sniffURL="http://web-sniffer.net/?url=".rawurlencode($uri)."&submit=Submit&http=1.1&gzip=yes&type=HEAD&ua=Mozilla%2F5.0+%28Windows%3B+U%3B+Windows+NT+5.1%3B+en-US%3B+rv%3A1.8.1%29+Gecko%2F20061010+Firefox%2F2.0+Web-Sniffer%2F1.0.24";
            echo("\nsniffURL=$sniffURL");
            $sniffing=file_get_contents($sniffURL);
            echo("\n\n\nsniffing=$sniffing");
            $before="Content-Type:</td><td>";
            $start=strrpos($sniffing,$before)+strlen($before);
            $after=strpos($sniffing,"</td>",$start);
            $mime=substr($sniffing,$start,$after-$start);
            echo ("\nstart=$start");
            echo ("\nafter=$after");
            echo ("\nmime=$mime");
           if (($mime=="image/svg+xml")&&($ext!="svg")) {echo("\n$uri");}
           if (($mime!="image/svg+xml")&&($ext=="svg")) {echo("ERROR");}
           if ($mime=="text/html"){
               //$content=$req->getResponseBody();
               $content=file_get_contents($uri);
               $extraLinks=addLinks($content,$level);
           }
       }
/*
    } catch (HttpException $ex) {
       echo $ex;
    }
}
*/
}
?>