paragraph1\phpFCM\Message::setCollapseKey PHP Method

See also: https://firebase.google.com/docs/cloud-messaging/concept-options#collapsible_and_non-collapsible_messages

public setCollapseKey ( string $collapseKey ) : Message
$collapseKey	string
return	Message

    public function setCollapseKey($collapseKey)
    {
        $this->collapseKey = $collapseKey;
        return $this;
    }

Message