foreach($thumbs as $v)
{
    $x = getMainColor($path.$v['dateiname'],100);
    $key = $t[0];
    
    $array[$key]['dateiname'] = $v['dateiname'];
    $array[$key]['art_id'] = $t[0];
    
    $array[$key]['r'] = $x['r'];
    $array[$key]['g'] = $x['g'];
    $array[$key]['b'] = $x['b'];
    unset($x);
}
// Multidimensionales Array füllen:
foreach ($array as $key => $row)
{
    $dateiname[$key]    = $row['dateiname'];
    $r[$key] = intval($row['r']);
    $g[$key] = intval($row['g']);
    $b[$key] = intval($row['b']);
}
// Sortierung
array_multisort($r, SORT_ASC, $g, SORT_ASC, $b, SORT_ASC, $array);