
Originally Posted by
kuroi
HTML is interpreted in your visitors' browsers. PHP runs on your server.
PHP does things that HTML simply can't do, like extract product information from your database and inserting it into HTML pages, or validating customers information before passing credit card transactions to payment gateways.
You don't have to use PHP to do these things, but if not you would need a different server side language and there are carts that use Ruby or PERL, but you'd probably find the learning curve for those even greater.
However, I'd recommend that you step back and examine your premise. Why does it matter that Zen Cart is written in PHP? There are an awful lot of people using it who know little or nothing about the programming language in which it's written, just like I don't need to know the details of how an internal combustion engine works to be able to fill my car with gas and drive it.