Plaintext/HTML Email doesn't work in mac mail client - php

Question

The code below is the code i am using. It works fine in thunderbird but not in mac mail client (and i assume anything made by microsoft. I currently do not have access to this to test it in). Much as i am aware of the idiosyncrasies of the various mail clients, I am flummoxed by this! It's fairly self explanatory but i am trying to send plain text and html emails to increase the readership. Any help would be much appreciated.
EDIT
I should have clarified that the contents get sent regardless but in thunderbird it displays the message correctly, but in mac mail client you get the entire thing from the first PHP-alt to the last PHP
<?php
//define the receiver of the email
$to = 'youraddress#example.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
$headers .= "\r\nContent-Type: multipart/alternative; boundary=\"PHP-alt-".$random_hash."\"";
//define the body of the message.
ob_start(); //Turn on output buffering
?>
--PHP-alt-<?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-alt-<?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-alt-<?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";
?>

Answer 1

Rather than try and roll your own mailer, try e.g. PHPMailer. It has very good support for multipart/alternative. It's much easier to integrate this than to roll your own solution. I've been there - after working endlessly around strange MIME problems, I've dropped my hand-made mailer, switched to this, and focused on other things in the time I've spared.
In other words, don't reinvent the wheel. Although doing it yourself can be a good challenge and you'll learn a lot during the process, if you just want it to work, these guys have dealt with the complexity for you.

Answer 2

You're not using output buffering correctly - see man page for ob_end_clean to see that it doesn't return the captured output, you need ob_get_contents for that:
$message =ob_get_contents();
ob_end_clean();