CodeIgniter don't error log rmdir, unlink, chmod, etc

// create MY_Log.php in folder application/libraries
<?php  if ( ! defined('BASEPATH')) exit('No direct script access allowed');

class MY_Log extends CI_Log
{
    public function write_log($level = 'error', $msg, $php_error = FALSE)
    {
        // strings that will not be saved in error log file
        $blacklist = array(
            'Severity: Warning  --> rmdir(',
            'Severity: Warning  --> unlink(',
            'Severity: Warning  --> chmod() ['
        );

        foreach ($blacklist as $str)
        {
            if (strpos($msg, $str) !== FALSE)
            {
                return TRUE;
            }
        }

        parent::write_log($level, $msg, $php_error);
    }
}