Problem (need how-to) "member_member_login_start"

I’m trying to write an extension so as to validate user against an external database, but I’m stuck. Here’s the code:

function member_member_login_start() //This function is called on event "member_member_login_start"
    {
                // QUERY FOR VALIDATING THE USER
                // USER IS VALIDATED FROM EXT DB SUCCESSFULLY

        if ($user_info['authenticated'])
        {
                        echo "auhtneicated";
                        print_r($this->EE->session->userdata);
                        exit;
                        
        }
        else
        {
                        exit('User authentication failed.');
        }
                
    }

So my questions are:

1. Even though I get a message user is authenticated successfully (EE message), the user details are not set in the EE session. When I print the user session array, it shows empty member_id and other fields. Do I need to set user data in session in my code?

2. How can I display the “authentication failed” message in the regular EE message box that comes if I enter wrong login details in normal scenario?

3. Where & how to use $EXT->end_script = TRUE; I saw it in docs but couldn’t understand how it is used?

Moved to Development and Programming by Moderator