Attach PDF through Email

I need to be able to allow a user to submit a PDF form online and use PHP to emial the PDF in its entirety.  I know that I can use the "SUBMIT" button functionality provided by Adobe, however, it is dependent on a client side email application like Outlook.  This PDF needs to be emailed indepedent.

I'm able to send email fine with PHP.  However, I have not stumbled across the code to attache the PDF file in the email.

I appreciate any assistance on this.