Sending an HTML with text alternative email with Zend\Mail

Sending a multi-part email with Zend\Mail is easy enough, but if you want to send an HTML email with a text alternative, you need to remember to set the content-type in the headers to multipart/alternative. As this is the second time I had to work this out, I’m noting it here for the next time I forget!

use Zend\Mail;
use Zend\Mime\Message as MimeMessage;
use Zend\Mime\Part as MimePart;


function sendMail($htmlBody, $textBody, $subject, $from, $to)
{
    $htmlPart = new MimePart($htmlBody);
    $htmlPart->type = "text/html";

    $textPart = new MimePart($textBody);
    $textPart->type = "text/plain";

    $body = new MimeMessage();
    $body->setParts(array($textPart, $htmlPart));

    $message = new MailMessage();
    $message->setFrom($from);
    $message->addTo($to);
    $message->setSubject($subject);

    $message->setEncoding("UTF-8");
    $message->setBody($body);
    $message->getHeaders()->get('content-type')->setType('multipart/alternative');

    $transport = new Mail\Transport\Sendmail();
    $transport->send($message);
}