/**
 * @param integer seconds
 * @return string human readable text
 */
function fuzzy_seconds($seconds)
{
	if ($seconds <= 0) return FALSE;

	$w = $seconds / 86400 / 7;
	$d = $seconds / 86400 % 7;
	$h = $seconds / 3600 % 24;
	$m = $seconds / 60 % 60; 
	$s = $seconds % 60;

	$output = array();

	if ($w >= 1) $output[] = "{$w} ".($w == 1 ? 'week' : 'weken');
	if ($d >= 1) $output[] = "{$d} ".($d == 1 ? 'dag' : 'dagen');
	if ($h >= 1) $output[] = "{$h} ".($h == 1 ? 'uur' : 'uren');
	if ($m >= 1) $output[] = "{$m} ".($m == 1 ? 'minuut' : 'minuten');
	if ($s >= 1) $output[] = "{$s} ".($s == 1 ? 'seconden' : 'seconden');

	return implode(', ', $output);
}

Resultaat:

echo fuzzy_seconds(123456);

1 dag, 10 uren, 17 minuten, 36 seconden