Script to test for server uptime [Magento]

test.php

<?php 
header("Cache-Control: no-cache, must-revalidate"); 
header("Expires: Sat, 26 Jul 1997 05:00:00 GMT");
header("Content-type: application/json");

require_once "app/Mage.php";

Mage::app($_SERVER['MAGE_RUN_CODE'], $_SERVER['MAGE_RUN_TYPE']);

$resource = Mage::getSingleton('core/resource');
$readConnection = $resource->getConnection('core_read');
$cfg = $readConnection->getConfig();
$conn = mysqli_connect($cfg['host'],$cfg['username'],$cfg['password']);

$connected = mysqli_ping($conn);

if($connected) {
        echo "I'm OK!";
} else {
        exit(1);
}