GNuPG Newb

 Hi,
 I'm trying to send a php mail form and not able to get it to encrypt or do much of anything.
 The mail form works on its own ,but when trying to add the GNuPG it doesnt work.

 I have the private and public key pair generated. My host has the GnuPG keys generated and the .gnupg bin etc.

 I was a bit confused because i heard that PGP can intercept a mail form through SMTP and encrypt it , but that GnuPG can not?

 Do i have to first output my mail form into a temp folder as a .txt file, and then encrypt the .txt file?

 the overview of the mail form , is that its coded in PHP, and the information in the mail will be populated by $_SESSION and $_POST information.
 It's an auto form that will automatically send the mail when user submits the last form, and is transferred to that last page.

 When reaching last page, the mail form is assembled and populated and sent.

 Currently it all works when using regular non-encryption mail)

Is there an easy way to take the existing mail form thats already working, and attach some code to have it encrypt with the private and public key pair?

Thank You!