common\models\User::findByUsername PHP Method

    public static function findByUsername($username)
    {
        return static::findOne(['username' => $username, 'status' => self::STATUS_ACTIVE]);
    }

 /**
  * Finds user by [[username]]
  *
  * @return User|null
  */
 public function getUser()
 {
     if ($this->_user === false) {
         $this->_user = User::findByUsername($this->username);
     }
     return $this->_user;
 }