You can use this simple code to test one proxy:
<?
$ip = "192.168.1.1";
$port = "80";
$curl = curl_init();
CURL_SETOPT($curl,CURLOPT_URL,"http://google.fr");
CURL_SETOPT($curl,CURLOPT_PROXY,$ip.":".$port);
CURL_SETOPT($curl,CURLOPT_PROXYTYPE,CURLPROXY_HTTP);
CURL_SETOPT($curl,CURLOPT_TIMEOUT,20);
CURL_SETOPT($curl,CURLOPT_RETURNTRANSFER,True);
CURL_SETOPT($curl,CURLOPT_FOLLOWLOCATION,True);
curl_exec($curl);
curl_close($curl);
?>
However, if you want to test multiple proxies, use the for loop to do that.