- floor: documentation ( source)
<?php
$local = new DateTimeZone('America/Los_Angeles');
$totSecs = $local->getOffset(new DateTime());
$totSecs -= .5 * 3600;
$hrs = floor($totSecs / (60 * 60));
$mins = floor(($totSecs - $hrs * 60 * 60) / 60);
echo $hrs . ':' . $mins;