foreach ($counts as $key => $value) {
    switch($key){
        case 'foo':
            $counts[$key]=function1($output[$key], $counts[$key]);
            break;
        case 'bar':
        case 'baz':
        case 'moep':
        case 'fluedeltuet':
            $counts[$key]=function2($output[$key], $counts[$key]);
            break;
        default:
            $counts[$key]=function3($output[$key], $counts[$key]);
    }
}