How can PHP developers effectively troubleshoot login issues, like being unable to access the admin area of a webshop, caused by cookie key or session management problems?

To troubleshoot login issues caused by cookie key or session management problems, PHP developers can start by checking if the session is being properly started and maintained. They should ensure that the cookie key used to store session information is consistent across the application. Additionally, developers should verify that the session is being properly destroyed after logout to prevent any conflicts.

// Start the session
session_start();

// Set a consistent cookie key for session storage
session_name('webshop_session');

// Destroy the session on logout
session_destroy();