yii\log\Target::getMessagePrefix PHP Method

    public function getMessagePrefix($message)
    {
        if ($this->prefix !== null) {
            return call_user_func($this->prefix, $message);
        }
        if (Yii::$app === null) {
            return '';
        }
        $request = Yii::$app->getRequest();
        $ip = $request instanceof Request ? $request->getUserIP() : '-';
        /* @var $user \yii\web\User */
        $user = Yii::$app->has('user', true) ? Yii::$app->get('user') : null;
        if ($user && ($identity = $user->getIdentity(false))) {
            $userID = $identity->getId();
        } else {
            $userID = '-';
        }
        /* @var $session \yii\web\Session */
        $session = Yii::$app->has('session', true) ? Yii::$app->get('session') : null;
        $sessionID = $session && $session->getIsActive() ? $session->getId() : '-';
        return "[{$ip}][{$userID}][{$sessionID}]";
    }