How can PHP developers avoid the "Notice: A session had already been started - ignoring session_start()" error when working with session variables in multiple objects?

To avoid the "Notice: A session had already been started - ignoring session_start()" error when working with session variables in multiple objects, PHP developers can check if a session has already started before calling session_start(). This can be done by using session_status() function to check if the session is active before starting a new one.

if (session_status() == PHP_SESSION_NONE) {
    session_start();
}