- abs: documentation ( source)
- strtotime: documentation ( source)
<?php
$startTime = strtotime('2016-06-02 00:27:00');
echo $startTime;
echo "\n\n";
$completeTime = strtotime('2016-06-02 00:55:42');
echo $completeTime;
echo "\n\n";
$totalMins = (int)(abs($startTime - $completeTime) / 60);
echo $totalMins;
echo "\n\n";
$finalPrice = $totalMins * 2;
echo $finalPrice;