code: public static function getExtensionOptions($optionName) {        
          //try yii2 params
          if (isset(Yii::$app->params['yii2-adldap-extension-Options']) &&
              is_array(Yii::$app->params['yii2-adldap-extension-Options']) && 
              array_key_exists($optionName, Yii::$app->params['yii2-adldap-extension-Options'])) 
          {
              return Yii::$app->params['yii2-adldap-extension-Options'][$optionName];
          }
          
          //default from distribution
          else if (array_key_exists($optionName, static::EXTENSION_OPTIONS_DEFAULT)) {
              return static::EXTENSION_OPTIONS_DEFAULT[$optionName];
          } 
          
          //Exception
          else {
              throw new \yii\base\Exception('Extension-Option ' . $optionName . ' not found. Please define settings in the config/params.php of the yii2 framework as described on top of the UserDbLdap.php');   
          }
      }
docs: Get a value of the group assignment options by option key.
  The options can be defined global in the yii2 params.php.
  If nothing is defined the defaults from the varibale EXTENSION_OPTIONS_DEFAULT
  are used.
  
  @param string $optionName The option key of the value to retrive.
  @return mixed The value of the option key
  @throws \yii\base\Exception if option key is not found in the given option set.