- var_dump: documentation ( source)
- round: documentation ( source)
<?php
$date = new DateTime('12:07 UTC');
$seconds = (int) $date->format('i');
$rounded = round($seconds / 5) * 5;
var_dump($date->format('H:i:s'));
var_dump($seconds);
var_dump($rounded);
$date->setTime($date->format('H'), $rounded, $date->format('s'));
var_dump($date->format('H:i:s'));