- array_map: documentation ( source)
- array_sum: documentation ( source)
- date: documentation ( source)
- strtotime: documentation ( source)
<?php
$times = ["1:10:12", "2:15:33", "3:12:10"];
$today = strtotime(date("Y-m-d"));
$intervals = array_map(function($a) use ($today){ return strtotime($a) - $today;}, $times);
echo array_sum($intervals)." Seconds";