Why am I getting the error "Class" app \ models \ Yii "not found"?

Question

The model function for which I received this error:

public function setPassword($password)
{
    $this->password_hash = Yii::$app->security->generatePasswordHash($password);
}

public function generateAuthKey()
{
    $this->auth_key = Yii::$app->security->generateRandomString();
}

Answer 1

Add

use Yii;

Before class declaration.

Or add a backslash before the word Yii.

$this->password_hash = \Yii::$app-> ...

Answer 2

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