Example 8-3 shows how the session_destroy( ) function is called. A session must be initialized before the session_destroy( ) call can be made. You should also test to see if $PHPSESSID is a set variable before killing the session. This prevents the code from creating a session, then immediately destroying it if the script is called without identifying a session. However, if the user has previously held a session cookie, PHP initializes the $PHPSESSID variable, and the code redundantly creates and destroys a session.
session_destroy function
session_destroy destroys all data registered to a session. To use the session variables again, session_start() function has to be called.
session_destroy() destroys all of the data associated with the current session but it does not unset any of the global variables associated with the session, or unset the session cookie.
Example 8-3. Ending a session
<?php
// Only attempt to end the session if there
// is a $PHPSESSID set by the request.
if(isset($PHPSESSID)) {
$message = "<p>End of session ($PHPSESSID).";
session_start( );
session_destroy( );
} else {
$message = "<p>There was no session to destroy!";
}
?>
<!DOCTYPE HTML PUBLIC
"-//W3C//DTD HTML 4.0 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd" >
<html>
<head><title>Sessions</title></head>
<body>
<?=$message?>
</body>
</html>
