HTML Email mixed (html & attachement) coming thoough as plain text - php

Question

I've got an HTML email being sent by PHP, with a pdf attached via base64 encoding. It all works, except the email comes through as plain text, so you see all HTML tags and base64 output - obviously not ideal. There must be something I'm missing here to ensure it gets read as HTML & attachment.
If anybody can help that would be fantastic!
My PHP:
<?php $to = $email;
$message = 'testing...';
$subject = 'Health Insurance Quote Request';
$headers = "From: Andy - CEO Health.com.au <" . strip_tags('info#health.com.au') . ">\r\n";
$headers .= "Reply-To: Andy - CEO Health.com.au <". strip_tags('info#health.com.au') . ">\r\n";
// boundary
$semi_rand = md5(time());
$mime_boundary = "==Multipart_Boundary_x{$semi_rand}x";
// headers for attachment
$headers .= "\nMIME-Version: 1.0\n" . "Content-Type: multipart/mixed;\n" . " boundary=\"{$mime_boundary}\"";
// multipart boundary
$email_message = "This is a multi-part message in MIME format.\n\n" . "--{$mime_boundary}\n" . "Content-Type: text/html; charset=\"iso-8859-1\"\n" . "Content-Transfer-Encoding: 7bit\n\n" . $message . "\n\n";
$email_message .= "--{$mime_boundary}\n";
//get PDF URL
$data = chunk_split(base64_encode(file_get_contents('http://example.com/doge.pdf')));
$email_message .= "Content-Type: {\"application/pdf\"};\n" . " name=\"$product\"\n" .
"Content-Disposition: attachment;\n" . " filename=\"$product\"\n" .
"Content-Transfer-Encoding: base64\n\n" . $data . "\n\n";
$email_message .= "--{$mime_boundary}\n";
mail($email, $subject, $email_message, $headers);
Example of output:
MIME-Version: 1.0
Content-Type: multipart/mixed;
boundary="==Multipart_Boundary_xc9c6c260d1e99ba11f86b40c6c7848e0x"
This is a multi-part message in MIME format.
--==Multipart_Boundary_xc9c6c260d1e99ba11f86b40c6c7848e0x
Content-Type: text/html; charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
testing...
--==Multipart_Boundary_xc9c6c260d1e99ba11f86b40c6c7848e0x
Content-Type: {"application/pdf"};
name="HeartPlus65"
Content-Disposition: attachment;
filename="HeartPlus65"
cwt/SGdVm9X6LXQwvq03c+afGdAA9NlSAk1G3NyG2S5pDSY+CycXKDnuBJ5gFRupvZva0H2CXQqA
t9M6DlWx646bhhsx8NXdde0ES4z+8FP03XNEWTPMc/lWObbIG4ET4qxQ57eCm1V8RZOOzqG6+pu7
mYERMqHobI26KpfZYx27x8ESi65xkqOYkdbFIJ1qm2HXUEGZC0B1Jr2c6qmHeo3VULGurdIKhERP
Q6EJqtQ6rrWPbLiqzHgOlVLrfaIU8Zxe2SUhi4QTauK9G0/qbmjb2TD0HNkakoNlLbDzCql32d4A
khPjiE9rBQZGOvRvtxnEaGAlXimw7Vp4tIsqkjkI2JQ1upHBRgTA31CjqPNBjdM9ISRKHl9MLvc0
LeZUH8J7GNA1R+8mJvqkR0p5f7LZEbSkt7c2fopKX79LsEe2O7nv6qzJrc1xGreCsS
....

Answer 1

It may be not having a -- at the end of the last boundary tag
ie $email_message .= "--{$mime_boundary}\n";
to $email_message .= "--{$mime_boundary}--\n";
I'm not sure it there is a difference between multipart/mixed and multipart/alternative but this works for me
# Setup mime boundary
$mime_boundary = 'Multipart_Boundary_x'.md5(time()).'x';
$headers = "MIME-Version: 1.0\n";
$headers .= "Content-Type: multipart/alternative; boundary=\"$mime_boundary\"\n";
$headers .= "Content-Transfer-Encoding: 7bit\n";
$body = "This is a multi-part message in mime format.\n\n";
# Add in plain text version
$body .= "--$mime_boundary\n";
$body .= "Content-Type: text/plain; charset=\"charset=us-ascii\"\n";
$body .= "Content-Transfer-Encoding: 7bit\n\n";
$body .= $text_content;
$body .= "\n\n";
# Add in HTML version
$body .= "--$mime_boundary\n";
$body .= "Content-Type: text/html; charset=\"UTF-8\"\n";
$body .= "Content-Transfer-Encoding: 7bit\n\n";
$body .= $html_content;
$body .= "\n\n";
#Attachments
if ($path!='' && $filename!=''){
$file_size = filesize($path.$filename);
$handle = fopen($path.$filename, "r");
$filecontent = fread($handle, $file_size);
fclose($handle);
$filecontent = chunk_split(base64_encode($filecontent));
$body .= "--$mime_boundary\n";
$body .= "Content-Type: application/octet-stream; name=\"".$filename."\"\r\n"; // use different content types here
$body .= "Content-Transfer-Encoding: base64\r\n";
$body .= "Content-Disposition: attachment; filename=\"".$filename."\"\r\n\r\n";
$body .= $filecontent."\r\n\r\n";
}
# End email
$body .= "--$mime_boundary--\n";