What best practices should be followed when accessing class instances stored in PHP sessions?

When accessing class instances stored in PHP sessions, it is important to ensure that the class definition is available before trying to access the instance from the session. This can be done by including the class file or using autoloading mechanisms. Additionally, it is good practice to check if the session variable containing the class instance exists before trying to access it to avoid errors.

// Check if the session is not already started
if (session_status() == PHP_SESSION_NONE) {
    session_start();
}

// Include the class definition file or set up autoloading

// Check if the session variable exists before trying to access the class instance
if (isset($_SESSION['myClassInstance'])) {
    $myClassInstance = $_SESSION['myClassInstance'];
    // Now you can work with $myClassInstance
} else {
    // Handle the case when the session variable is not set
}