Mail Service using Singleton Design Pattern in PHP

Today, I am implementing a Mail Service class using the Singleton Design Pattern in PHP. In many applications, there are frequent email-sending operations, like on an e-commerce website, where an email is sent to the user after they place an order.

Using a Singleton pattern here allows the application to create only a single instance of the mail service connection. This enhances application performance by ensuring only one connection instance is maintained.

Please see the code below:

    // Chúng ta có thể cấu hình namespace cho ok hơn, vì mình test nên để require_once đến thư viện
    require_once "../../../vendor/autoload.php";
    use Symfony\Component\Mailer\Transport;
    use Symfony\Component\Mailer\Mailer;
    use Symfony\Component\Mime\Email;
    use Twig\Environment;
    use Twig\Loader\FilesystemLoader;
    class MailService{
        private static $instance = null;
        private $transport = null;
        private $mail_from = ""; // email
        private $pass = ""; // password
        private $mailer = null;
        private function __construct(){
            try { 
                $this->transport =Transport::fromDsn("smtp://{$this->mail_from}:{$this->pass}@smtp.gmail.com:587?encryption=tls");

                $this->mailer = new Mailer($this->transport);
            } catch (\PDOException $e) {
                throw new Exception($e->getMessage());
            }
        }

        public static function getInstance(){   
            if(self::$instance === null){
                // begin create instance
                self::$instance = new MailService();
            }
            // create instance object
            return self::$instance;

        }

        public function sendEmail(Array $data) : Array{
            try {
                $email = new Email();
                $email->from($this->mail_from);
                $email->to($data['email']);
                $email->subject($data['subject']);
                $email->text($data['message']);
                if($data['file'] != null){
                    $email->attachFromPath($data['file']);
                }
                $this->mailer->send($email);
                $data['status'] = 'success';
                return json_decode(json_encode($data), true, 512, JSON_THROW_ON_ERROR);
            }
            catch (\Exception $e) {
                $data['status'] = 'error';
                $data['message'] = $e->getMessage();
                return json_decode(json_encode($data), true, 512, JSON_THROW_ON_ERROR);
            }

        }

    }

Great! Now that the Singleton pattern is set up for the Mail Service, we can use it in our application. Here’s how you can integrate and use the Mail Service Singleton:

$mail = MailService::getInstance();
$mail2 = MailService::getInstance();

var_dump($mail === $mail2); //true
$mail->sendEmail([
    'subject' => 'LẬP TRÌNH WEBSITE | HOANGUYENIT',
    'email' => '[e-mail]',
])

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