public function adjustVolume(int $adjust): SpeakerInterface
    {
        $speakers = $this->getSpeakers();
        foreach ($speakers as $speaker) {
            $speaker->adjustVolume($adjust);
        }

        return $this;
    }
public function adjustVolume(int $adjust): SpeakerInterface
    {
        $speakers = $this->getSpeakers();
        foreach ($speakers as $speaker) {
            $speaker->adjustVolume($adjust);
        }

        return $this;
    }
public function adjustVolume ( int $ adjust ) : SpeakerInterface { $ speakers = $ this -> getSpeakers ( ) ; foreach ( $ speakers as $ speaker ) { $ speaker -> adjustVolume ( $ adjust ) ; } return $ this ; }
Adjust the volume of all the speakers this controller manages.

@param int $adjust The amount to adjust by between -100 and 100

@return $this
Adjust the volume of all the speakers this controller manages .