Sending multipart/alternative with PHP mail() - php

Question

So I am trying to send a fairly simple HTML email using PHP. I have spent the last three days trying to find a good solution and think I found one, but when I test it, it doesn't send properly. I borrowed this code from one of the tutorials I was referencing. The test code is as follows:
<?php
//define the receiver of the email
$to = 'myemail#gmail.com';
//define the subject of the email
$subject = 'Test HTML email';
//create a boundary string. It must be unique
//so we use the MD5 algorithm to generate a random hash
$random_hash = md5(date('r', time()));
//define the headers we want passed. Note that they are separated with \r\n
$headers = "From: webmaster#example.com\r\nReply-To: webmaster#example.com";
//add boundary string and mime type specification
$headers .= "\r\nContent-Type: multipart/alternative; boundary=\"".$random_hash."\"";
//define the body of the message.
ob_start(); //Turn on output buffering
?>
--<?php echo $random_hash; ?>
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Hello World!!!
This is simple text email message.
--<?php echo $random_hash; ?>
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
<h2>Hello World!</h2>
<p>This is something with <b>HTML</b> formatting.</p>
--<?php echo $random_hash; ?>--
<?
//copy current buffer contents into $message variable and delete current output buffer
$message = ob_get_clean();
//send the email
$mail_sent = #mail( $to, $subject, $message, $headers );
//if the message is sent successfully print "Mail sent". Otherwise print "Mail failed"
echo $mail_sent ? "Mail sent" : "Mail failed";
?>
The problem is that, although it sends the email just fine, it either sends it as plain text, or a blank message in Gmail. Any ideas why?

Answer 1

I should of course tell you to use a library for this, such as swift, but I think this is a good exercise so I'll tell you what's wrong with it :)
It's because your line endings are wrong. Unless otherwise specified, line endings in email messages are CRLF (\r\n), whereas your ob_start() block is likely to only have LF (\n) as the line separator.
This causes GMail to misinterpret the email message and shows nothing instead. In my case it shows an empty download file ;)