how to get email address with gmail api code example

Example: google client php get inbox messages

$optParams = [];
        $optParams['maxResults'] = 5; // Return Only 5 Messages
        $optParams['labelIds'] = 'INBOX'; // Only show messages in Inbox
        $messages = $service->users_messages->listUsersMessages('me',$optParams);
        $list = $messages->getMessages();
        $messageId = $list[0]->getId(); // Grab first Message


        $optParamsGet = [];
        $optParamsGet['format'] = 'full'; // Display message in payload
        $message = $service->users_messages->get('me',$messageId,$optParamsGet);
        $messagePayload = $message->getPayload();
        $headers = $message->getPayload()->getHeaders();
        $parts = $message->getPayload()->getParts();

        $body = $parts[0]['body'];
        $rawData = $body->data;
        $sanitizedData = strtr($rawData,'-_', '+/');
        $decodedMessage = base64_decode($sanitizedData);

        var_dump($decodedMessage);