From brokenpoet.org wiki

This page is very simple test of the fsockopen function. If it is functioning then it should say UP (the ip is google.com).

testfsockopen.php

<?php
$fp=@fsockopen ("74.125.67.100", 80, $errno, $errstr, 30);
if (!$fp) {
         echo "Down\n";
}
else {
         echo "Up\n";
         fclose ($fp);
}
?>