"session_start(): Ignoring session_start() because a session is already active," the message you're seeing, is a PHP warning message. It happens when you try to create a new session with the session_start() function but there is already an active session.

A session is a method of storing information (variables, user data, etc.) for a certain user across numerous pages or requests. When a session is started using session_start(), PHP generates a unique session ID for the user and transmits it to the user's browser as a cookie. The browser sends the session ID back to the server on subsequent requests, allowing PHP to resume the session and access the saved data.

When you call session_start() on a page where a session has already been established, the warning message appears. This can happen if your code contains numerous calls to session_start(), or if you include or need a script that also calls session_start().

You can take the following action to dismiss this warning:

1. Make careful to only call session_start() once, at the beginning of your script or on your application's main entry point.
   
2. Before invoking session_start(), check to see if a session is already active:
   

This code snippet prevents the warning by checking if a session is currently active before establishing a new one.

Examine your code to ensure that you are not calling session_start() more than once in various portions of your application.

You can avoid the "Ignoring session_start() because a session is already active" warning notice in your PHP application by following these instructions.