On successful login the user information will be stored in Yii::$app->user->identity variable. The authenticated user identity information can be retrieved via Yii::$app->user->identity
//To get whole logged in user data
$user = \Yii::$app->user->identity;
//To get id of the logged in user
$userId = \Yii::$app->user->identity->id
//To get username of the logged in user
\Yii::$app->user->identity->username
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