// Default usage:
$array = [ 1, 2, 3 ];
$value = $array
    $> array_map($$, 'callback')
    $> array_filter();

// With objects:
$object = new Clock;
$object
    $> setHour(12)
    $> setMinute(40)
    $> setSeconds(25)

    // It should run global callback($object) or $object->callback($object)?
    $> callback($$)
;