create short object

hi guys

i saw some one use app() instead of Yii::$app

How is this possible? and how to use it

Yii::app() is for Yii1 and Yii::$app is for Yii2.

Yes I know but i saw app()->user->id in yii2

Yii::$app convert to app()

its likely that app() function is defined by user to wrap Yii::$app which in return enable the following app()->user->id in yii2, where did you see it in craftcms?

It is just a shortcut. I use lot of such procedural functions. Here is couple examples:

function set_flash($value, $key = 'success') {

    Yii::$app->session->setFlash($key, $value);



function can($permissionName, $params = [], $allowCaching = true) {

    return Yii::$app->user->can($permissionName, $params, $allowCaching);


if(can('admin') && !is_role('moderator')) {


function assign_role($user_id, $role) {

    $auth = \Yii::$app->authManager;

    $authorRole = $auth->getRole($role);

    $auth->assign($authorRole, $user_id);



function is_guest() {

    return Yii::$app->user->isGuest;





This functions included in index.php file so they can be accessed in whole project.

But app() instead of Yii::$app looks like for very lazy guy )