- substr: documentation ( source)
- var_dump: documentation ( source)
<?php
$sting = "15.10.15 10:20";
$date = '20'.substr($string, 6, 2).'-'.substr($string, 3, 2).'-'.substr($string, 0, 2).' '.substr($string, 9, 2).':'.substr($string, 12, 2).':00';
var_dump( new \DateTime($date, new \DateTimeZone('UTC')));;