Bot code

public function newMemberUsername() {
    if ( isset( $this->data['message']['new_chat_participant']['first_name'] ) ) {
        return $this->data['message']['new_chat_participant']['first_name'];
    }

    return false;
}

public function leftMemberUsername() {
    if ( isset( $this->data['message']['left_chat_participant']['first_name'] ) ) {
        return $this->data['message']['left_chat_participant']['first_name'];
    }

    return false;
}

$newMember  = $telegram->newMemberUsername();
$leftMember = $telegram->leftMemberUsername();

switch ( true ) {
    case $newMember != false:
        if ( isset( $helloStickers[ $newMember ] ) ) {
            $sticker = $helloStickers[ $newMember ];
            $telegram->sendSticker( $sticker, null, null, $telegram->getMessageId() );
        } else if ( isset( $VIPHelloMessages[ $newMember ] ) ) {
            $message = $VIPHelloMessages[ $newMember ];
            $telegram->sendTextMessage( $message, null, null, null, null, $telegram->getMessageId() );
        } else {
            $n       = rand( 1, count( $helloMessages ) ) - 1;
            $message = str_replace( ':user:', $newMember, $helloMessages[ $n ] );
            $telegram->sendTextMessage( $message, null, null, null, null, $telegram->getMessageId() );
        }
        break;

    case $leftMember != false:
        if ( isset( $byeStickers[ $leftMember ] ) ) {
            $sticker = $byeStickers[ $leftMember ];
            $telegram->sendSticker( $sticker, null, null, $telegram->getMessageId() );
        } else if ( isset( $VIPByeMessages[ $leftMember ] ) ) {
            $message = $VIPByeMessages[ $leftMember ];
            $telegram->sendTextMessage( $message, null, null, null, null, $telegram->getMessageId() );
        } else {
            $n       = rand( 1, count( $byeMessages ) ) - 1;
            $message = str_replace( ':user:', $leftMember, $byeMessages[ $n ] );
            $telegram->sendTextMessage( $message, null, null, null, null, $telegram->getMessageId() );
        }
        break;