<?php
$date = '2014-04-11 18:20:20';
$timeInPast = strtotime($date); // date should be in YYYY-DD-MM HH:MM:SS format
$result = $currentTime - $timeInPast;
echo $result;
PD9waHAKCiRkYXRlID0gJzIwMTQtMDQtMTEgMTg6MjA6MjAnOwokY3VycmVudFRpbWUgPSB0aW1lKCk7CiR0aW1lSW5QYXN0ID0gc3RydG90aW1lKCRkYXRlKTsgLy8gZGF0ZSBzaG91bGQgYmUgaW4gWVlZWS1ERC1NTSBISDpNTTpTUyBmb3JtYXQKCiRyZXN1bHQgPSAkY3VycmVudFRpbWUgLSAkdGltZUluUGFzdDsKZWNobyAkcmVzdWx0Ow==