Javascript: If undefined or null or string length equals zero return false

function checkExists(myVar) {

 if (typeof myVar === 'undefined')  { return false;  }
 if ( myVar === null )      { return false;  }
 if ( myVar.length == 0)            { return false; } 
 
 return true;
 
}

PHP disk_free_space

$diskFreeSpace = round(disk_free_space($data_drive) / 1024 / 1024 / 1024);

Nice little uptimeRobot alert script:

isset($_REQUEST['threshold']) ? $driveThresold=$_REQUEST['threshold'] : $driveThresold=11; 
   
function killMe($input) { 
   header('HTTP/1.1 500 Internal Server Error'); 
   die();
}

function allGood($input) { 
   header("Content-Type:text/plain") ;
   die($input);
}

$diskFreeSpace = round(disk_free_space($data_drive) / 1024 / 1024 / 1024);
$diskfreespace < $driveThresold ? killMe($diskfreespace) : allGood(strval($diskfreespace));
die();

Directory List to XML

<?php
header("Content-type: text/xml");
print "<?xml version='1.0' encoding='UTF-8'?>\n<response?>\n";
$files = glob('*.xml');
foreach($files as $file) {
 print "<file?>".$file."</file?>\n<!-- ".date("F d Y H:i:s.",filemtime($file))."--?>\n";
}
die('');
?>