Question

So as a engineer, I usually require a concert understanding to be able to work with something. I feel like I understand the basics of a session. I am wondering about the specifics and details there of.

What are the limitations of a session?

How can I manipulate a session? What can explicitly not be done to or with a session.

What data structures does PHP use to define and manage sessions?

Is a PHP session different from any other session in any significant way?

I understand that these questions are general, so if anyone can simply suggest a good resource I would be thankful. There is plenty of info out there, but it is either too basic or teaching to a specific topic.

Thank you for the help.

Answer 1

Sessions is a way for the server to recognize you so he sends to you a customized version of the page instead of sending always the same page for everybody.

To recognize you one way is he tells the browser to save in your computer a small file with a simple text, and when you visit the page again the server would ask the browser for that file, if the browser sends it, and it contains the expected content, the server can now know this is you again. That are cookies.

Another way to maintain a session, a part from cookies, is the server puts a special unique token for you in the url of all the links the page has. Whenever you browse the site all pages you visit will have that token, the server see it and know it’s the token it made to you, so he knows it’s you again.

So both with cookies or url-based sessions, the server will have to save info about the sessions opened, for example to store the $_SESSION variables you create in PHP, if you create such a variable the server will save it to a file which he will later identified by your cookie or token content and when you re-visit the page he will read that file and load the $_SESSION variables you create last time.