calling javascript functions inside PHP

I use a PHP self-validating form for taking orders off my site. (on submit it calls itself and if there are no errors a send variable is set and it emails me the information, etc - standard stuff). I'd like to start taking CC orders and would like to encode the information using javascript http://javascript.internet.com/passwords/virgenere-encryption.html. I'll use a hidden value as a codephrase to encode the CC number, then when I receive the order I can go to a secure page on the site to decrypt it. The question is - how do I call a javascript function from my PHP code? I want to do the encoding just before I email the form variables. ie - if ($send == "yes"){ do javascript encoding of cc number $mail (information to me) echo ("Your Order has been sent") } Thanks for any help, Dean