Soma Horas

<?php

function somarHoras(array $times) {

    $seconds = 0;

    foreach ($times as $time) {
        list( $g, $i, $s ) = explode(':', $time);
        $seconds += $g * 3600;
        $seconds += $i * 60;
        $seconds += $s;
    }

    $hours = floor($seconds / 3600);
    $seconds -= $hours * 3600;
    $minutes = floor($seconds / 60);
    $seconds -= $minutes * 60;

    $seconds = ($seconds == 0 || $seconds <= 9) ? "0{$seconds}" : $seconds;
    $minutes = ($minutes == 0 || $minutes <= 9) ? "0{$minutes}" : $minutes;
    $hours = ($hours <= 9) ? "0{$hours}" : $hours;

    return "{$hours}:{$minutes}:{$seconds}";
}

$times = [
    '01:31:22',
    '03:29:38',
];
echo somarHoras($times);