Accessing ajax/REST based php api

Question

Someone built a site using joomla and third party plugin RS Forms Pro and created a page where a client could configure and purchase a product (via stripe). But they have asked me to write some scripts that allows them to create a basket system so clients can buy multiple products at once without entering their card details each time.

I have years of php/js experience but have never worked with a system like joomla. RSForms Pro allows me to attach javascripts and attributes to form items so this looked very easy and the JS part has indeed been simple. However, I wrote a small PHP shopping cart designed to be interfaced via GET url params and there is no where on the webserver I can place it where attempting an ajax request does not cause a 403 forbidden error.

What is the path of least resistance is to get the php api I've written into the joomla ecosystem in a way that will allow me to talk with it properly from within RSForms pages? Many thanks.

EDIT for functional details: The php script I wrote stores item data (class objects in this case) in a php session, it's essentially a simple session cart. The script itself expects to find instructions passed via URL, such as script.php?additem&itemdata=foobar which the script reads from the standard $_GET array. The script echo's a result which can either be some requested data, a confirmation or an error string - in all cases designed to be processed by the calling javascript.

Answer 1

We have minimum information about how you have implemented all the above, however, I guess that you have created a php script somewhere that won't be executed/accessed from within Joomla's execution flow, but you are calling it directly. Right? In this case, you skip Joomla, the 403 error you get isn't coming from Joomla. Most likely this is a security restriction (access forbidden error) from your server.

Usually this comes either from directives in the .htaccess file - e.g. restricting the direct access/execution of php files, or by other security mechanisms/firewalls e.g. mod_security - which has become a standard in many hosting environments.

As for if you wanted to go fully the Joomla way, you would want to write a Joomla extension for your application.