if (!$this->_check($msg)) {
            $this->error = $msg;
            return false;
        }
    }
    //This deletes any messages marked for deletion, and then logs you off of the mail server.
    //This is the last command to use. This does not disconnect you from the ISP, just the mailbox.
    public function pQUIT()
    {
        $this->_write('QUIT');
        $msg = $this->_read();
        if (!$this->_check($msg)) {
            $this->error = $msg;
            return false;
        }
    }
    public function __destruct()
    {
        fclose($this->fd);
    }
}
//EXAMPLE:
$pop3 = new POP3();
$pop3->pUSERPASS('tieto', '123456');
if ($pop3->error) {
    echo 'ERROR: ' . $pop3->error;
    exit(0);
}
$messages = $pop3->pLIST();
echo $pop3->pRETR(1);
$pop3->pQUIT();