A quick snippet to ping an address with a port with PHP.

serverpinger.php

//These values will ping a minecraft server (I've chosen some random dedi-server here)
$address = "mc.pewpew.dk";
$port = 25565;
$timeout = 3; //3 seconds before giving up
$fp = fsockopen($address,$port,$errno,$errstr,$timeout);
if(!$fp)
{
	echo "fail";
}
else
{
	fclose($fp);
	echo "success";
}
//You could use these for a minecraft server status thing