Paypal Back End Programming

[BusinessStudent]

Hello to everyone on the Compsci.ca boards, I had a question regarding the site PayPal.com

I know that these forums emphasize more on software programming, (C,C#,C++,Java) but I was wondering if somebody
could give me insight on the back end programming done on PayPal's site. Of course I know that CSS/xhtml is on the front end and that it is not programming, but
what server side programming do they use to run/transfer money effectively and safely through security encryption. It might just be PHP, but I am not particularly certain.
If anyone could provide feedback that would be great.

BTW - My reasons for wanting to know seem very general and odd but do trust that I am just interested in their operations of how their site works.

Thanks

[jbking]

Paypal's Sample code notes PHP, Java and ASP.Net examples, so there is some code on their site of each of those categories for one theoretical answer to the question.

Paypal's URLs seem to suggest they use some form of CGI, which could be Perl, C, or C++ for a few possiblities.