<?php

interface Sending
{
    public function send($email);
}

class MailerAdapter implements Sending
{
    private $transport;

    public function __construct($name = 'Mailgun')
    {
        $this->setTransport($name);
    }

    public function setTransport($name)
    {
        $this->transport = new ($name . 'Transport');
    }

    public function send($email)
    {
        $this->transport->send($email);
    }
}

class MailgunTransport implements Sending
{
    private $mailgun_api;

    public function __construct()
    {
        $this->mailgun_api = Mailgun::create($_ENV['MAILGUN_KEY']);
    }

    public function send($email)
    {
        $this->mailgun_api->send($email);
    }
}

class MailjetTransport implements Sending
{
    private $mailjet_api;

    public function __construct()
    {
        $this->mailjet_api = new mailjet();
    }

    public function send($email)
    {
        $this->mailjet_api->send($email);
    }
}

$mailer = new MailerAdapter();
$mailer->setTransport('Mailgun');
$mailer->send('mon email');