Add custom php logic file to Wordpress

Question

I'm looking for a simple solution to add a custom php file and route to a Wordpress website.

Let's say I have a page with a simple form. I want submit that form through ajax and handle the form submission myself in a custom php file. Basically I just want to create a simple route where I can put all the logic and output a json in return.

Wordpress is kinda new to me, I was wondering, what's the best way to achieve that ?

edit:

I would like to add an url like http://mywebsi.te/validate that redirect to validate.php and output a json file from there.

Answer 1

You can do something like this :--

http://codex.wordpress.org/Page_Templates

Hope this will help you...