Do AJAX requests retain PHP Session info?

Question

If I had a user logged onto my site, having his id stored in $_SESSION, and from his browser he clicked a 'Save' button which would make an AJAX request to the server. Will his $_SESSION and cookies be retained in this request, and can I safely rely on the id being present in the $_SESSION?

Answer 1

The answer is yes:

Sessions are maintained server-side. As far as the server is concerned, there is no difference between an AJAX request and a regular page request. They are both HTTP requests, and they both contain cookie information in the header in the same way.

From the client side, the same cookies will always be sent to the server whether it's a regular request or an AJAX request. The Javascript code does not need to do anything special or even to be aware of this happening, it just works the same as it does with regular requests.