Javascript: User Authentication via Session

This snippet demonstrates how to implement a user authentication system using PHP sessions. It starts by checking if a session is already started and then processes user login by verifying credentials against a database.

The code provides a secure way to handle sessions by regenerating session IDs upon successful login. It helps in preventing session fixation attacks. The logout function clears the user's session and destroys it.

For additional security, the script uses password hashing with PHP's built-in functions. It ensures that user passwords are not stored in plain text in the database.

Error handling is integrated to manage cases where the login fails due to incorrect credentials or other issues. It gives feedback to the user without exposing sensitive system information.

The snippet is adaptable to various frameworks and CMS by changing the database connection and query parts according to the specific application's architecture.