A PHP session variable is used to store information about, or change settings for a user session.
Session variables hold information about one single user, and are available to all pages in one
When you are working with an application, you open it, do some changes and then you close it.
This is much like a Session. The computer knows who you are. It knows when you start the
application and when you end. But on the internet there is one problem: the web server does not
know who you are and what you do because the HTTP address doesn't maintain state.
A PHP session solves this problem by allowing you to store user information on the server for
later use (i.e. username, shopping items, etc). However, session information is temporary and
will be deleted after the user has left the website. If you need a permanent storage you may
want to store the data in a database.
Sessions work by creating a unique id (UID) for each visitor and store variables based on this
UID. The UID is either stored in a cookie or is propagated in the URL.
Before you can store user information in your PHP session, you must first start up the
Note: The session_start() function must appear BEFORE the <html> tag:
The code above will register the user's session with the server, allow you to start saving user
information, and assign a UID for that user's session.
The correct way to store and retrieve session variables is to use the PHP $_SESSION variable:
In the example below, we create a simple page-views counter. The isset() function checks if the
"views" variable has already been set. If "views" was set, we can increment
our counter. If "views" doesn't exist, we create a "views" variable, and set
it to 1:
If you wish to delete some session data, you can use the unset() or the session_destroy()
The unset() function is used to free the specified session variable:
You can also completely destroy the session by calling the session_destroy() function:
Note: session_destroy() will reset your session and you will lose all your stored session
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