Understanding the Distinction between session_unset() and session_destroy() in PHP

The PHP functions session_unset() and session_destroy() serve different purposes in managing session data. Despite their apparent similarity in clearing session variables, they have distinct effects.

Difference between session_unset() and session_destroy()

• session_unset(): This function removes all variables stored in the $_SESSION superglobal array. It effectively "unsets" the variables without impacting the session data in the session storage.
• session_destroy(): In contrast, session_destroy() deletes the entire session data from the session storage. This means all session variables, including those stored in the $_SESSION array, are destroyed.

Impact on Session Cookie

Neither session_unset() nor session_destroy() deletes the session cookie from the client's browser. The cookie is a flag used to identify the session, even if the session data has been cleared or destroyed.

Destroying a Session

To terminate a PHP session, including both session data and the session cookie, you need to perform the following steps:

1. Call session_destroy() to delete the session data.
2. Use the setcookie() function to expire the session cookie.

session_destroy();
setcookie(session_name(), '', time() - 3600);

This will effectively end the session for the user.