<?php

class Qs_Time
{
    public static function durationToString($duration)
    {
        $parts = [];
        $days = floor($duration/(24 * 60 * 60));
        $hours = floor(($duration - $days * 24 * 60 * 60) / 60 / 60);
        $minutes = floor(($duration - $days * 24 * 60 * 60 - $hours * 60 * 60) / 60);
        $seconds = floor(($duration - $days * 24 * 60 * 60 - $hours * 60 * 60 - $minutes * 60));

        foreach (['days' => 'd', 'hours' => 'h', 'minutes' => 'm', 'seconds' => 's'] as $name => $unit) {
            if (!$$name) {
                continue;
            }
            $parts[] = sprintf('%02d%s', $$name, $unit);
        }
        return implode(' ', $parts);
    }
}