How to call a PHP function in JavaScript?

Answer 1

Basically, you are mixing server-side (PHP) and client-side (JS) scripting.

It is however possible - thanks eg. to AJAX. Because you was not specific about what do you exactly need to be done after the select box changes, I can only point you to some resources and propose following:

• learn and start using jQuery (jquery.com) - it will help you get started and maintain cross-browser compatibility,
• learn how to make AJAX requests (eg. in the function you just were firing when onchange event was fired) - eg. using .post() jQuery function,
• learn how to return data from PHP (eg. using json_encode() in PHP, but raw HTML is also ok) and use it in JS,