can session variables survive from php -> html -> php?

the question is really simple, but i searched it many different ways and the results were not related t开发者_运维百科o my question.

so if i have a session variable in a php file if i open an html page after that and then a php file again, will i be able to retrieve the data ? or do they all have to be adjacent?

I tried php->html->php but i couldn't get the variables on the other side. maybe Im doing something wrong.

Thanks in advance

Not 100% sure what you mean, but if by "open" you mean in the browser, the calls do not need to be adjacent. You just need to do a session_start() in every PHP script in which you want to use session data.

Adjacency is not something that is really relevant for this question.

in PHP way of things, sessions are essentially files that contain serialized data on the server. The browser that called a script containing session_start() call receives a special token that identifies the session on the server, and it is normally (though not necessarily) stored as a cookie.

This effectively means that any php script that uses session_start() and receives a session id (via cookie or otherwise) will read and could use session data, unless it was removed from the server file system between the calls, or the session has expired (frankly, I'm not sure whether PHP removes the expired sessions on the server side).

Accessing anything outside of this model with the browser (html page, or even other sites) will not affect it in any way, unless these actions change or remove session id.

yes...session variable can survive php->html->php.

But on every php page ...very first line should be session_start()

This easy way (I guess): Set a cookie storing the session ID on the first php page. This way, every other php page can access the session ID and use it to restore the stored data, not matter how many (even foreign) pages were in between.