Sessions are used to store information which can be used through-out the application for the entire time the user is logged in or running the application. Each time a user visits your website, you can create a session for that user to store information pertaining to that user.
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.
Starting a PHP Session
Now lets learn how we create a session in PHP.
Before you can store any information in session variables, you must first start up the session using the session_start() function. See below.
Note: The session_start() function must appear BEFORE the <html> tag:
Storing information in a session
To store information is a session variable, you must use the predefined session variable $_SESSION.
Now, as an example, lets store user’s name and their age in a session. To do so you would do the following.
$_SESSION["username"] = "qpt";
$_SESSION["age"] = "25";
Retrieving stored session information
Retrieving stored session information is really easy. You can access the stored session information on any page without doing anything extra.
The output of the code above could be something like this:
Destroying/deleting session information
Remember sessions are destroyed automatically after user leaves your website or closes the browser, but if you wish to clear a session variable yourself, you can simple use the unset() function to clean the session variable.
To completely destroy all session variables in one go, you can use the session_destroy() function.
Note: session_destroy() will reset your session and you will lose all your stored session data.