Session Intercepting Filter weirdness

[mijokijo]

Hey all, I'm experiencing unexpected behavior from a session IF.

<?php

class SessionFilter
{
    public $nextfilter;
    
    public function __construct($nextfilter)
    {
        $this->nextfilter = $nextfilter;
    }
    
    public function execute()
    {
        if(!isset($_SESSION['user_name'])) // <--- This part
        {
            session_start();
            $_SESSION['user_name'] = 'Anonymous';
            $_SESSION['alias'] = 'Anonymous';
            $_SESSION['plevel'] = '0';
            $_SESSION['loggedin'] = FALSE;
        } else {
            session_start();
        }
        
        $this->nextfilter->execute();
    }
}

?>

When I login in, the $_SESSION is set. When I go back to my front page, It doesn't seem to remember me. It has the $_SESSION['user_name'] set to Anonymous. It ran the filter even though the $_SESSION['user_name'] variable was already set, the exact opposite of what I wanted. However:

<?php

class SessionFilter
{
    public $nextfilter;
    
    public function __construct($nextfilter)
    {
        $this->nextfilter = $nextfilter;
    }
    
    public function execute()
    {
        if(isset($_SESSION['user_name'])) // <--- Notice isset rather than !isset
        {
            session_start();
            $_SESSION['user_name'] = 'Anonymous';
            $_SESSION['alias'] = 'Anonymous';
            $_SESSION['plevel'] = '0';
            $_SESSION['loggedin'] = FALSE;
        } else {
            session_start();
        }
        
        $this->nextfilter->execute();
    }
}

?>

Does what I want, but exactly the opposite of what I expected. Not only that, but when I go to my front page, the $_SESSION['user_name'] is the same as it was set when I logged in. That means that is isset, rather than !isset.

Maybe I'm doing this the wrong way? I'm not very experienced with sessions, so there could be somehting I'm missing.

Hope I was able to communicate my problem clearly.

[Ren]

Have to call session_start() before using $_SESSION.

[sleepeasy]

call session_start() before you start using $_SESSION:

public function execute() { 
    if (session_id() == NULL) {
        session_start();
    }
    if(!isset($_SESSION['user_name'])) { 
        $_SESSION['user_name'] = 'Anonymous'; 
        $_SESSION['alias'] = 'Anonymous'; 
        $_SESSION['plevel'] = '0'; 
        $_SESSION['loggedin'] = FALSE; 
    }
         
    $this->nextfilter->execute(); 
} 

[mijokijo]

Thanks for the info guys.