$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, "http://site.ru");
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_HEADER, 0);
$output = curl_exec($ch);
curl_close($ch);
t1 = microtime(true);
$output = curl_exec($ch);
t2 = microtime(true);