- method_exists: documentation ( source)
<?php
if( method_exists('DateTime', 'diff') ){
$zone = new DateTimeZone('Europe/Madrid');
$start = new DateTime('2013-03-31 1:59:00 ', $zone);
$end = new DateTime('2013-03-31 3:00:00', $zone);
$difference = $start->diff($end);
$cet = $difference->format('%H:%I:%S');
echo "CET: $cet\n";
$start->setTimeZone(new DateTimeZone('UTC'));
$end->setTimeZone(new DateTimeZone('UTC'));
$difference = $start->diff($end);
$utm = $difference->format('%H:%I:%S');
echo "UTM: $utm\n";
echo ($cet===$utm ? 'Correct' : 'Error') . "\n";
}else{
echo 'DateTime::diff() no available yet';
}