Can't seem to write to LOG...

[eluser]duartix[/eluser]
I'm using PHP 5.5.1 and CodeIgniter 2.1.4-

On one of my controllers, I've got the following code:

Code:

public function logout() {
        error_log("LOGOUT!");
    }

The problem is that this "LOGOUT!" message never appears in my log file: C:\xampp\htdocs\glup2\application\logs\log-2013-11-14.php

I've tried raising the error log threshold, but it's still not working.
My config.php is as follows:

Code:

$config['log_threshold'] = 4;
$config['log_path'] = '';
$config['log_date_format'] = 'Y-m-d H:i:s';

All sorts of debug messages (like class loading and helper loads) get to the log, but not my LOGOUT message.
Any ideas on what I'm doing wrong?
TIA.

[eluser]duartix[/eluser]
Solved.
Switched from error_log (PHP) to log_message (CodeIgniter).
It's working now.