code: protected function loadWsdl($params)
      {
          if (isset($params['wsdl'])) {
              if (is_string($params['wsdl'])) {
                  $this->wsdl = [
                      $params['wsdl']
                  ];
              } elseif (is_array($params['wsdl'])) {
                  $this->wsdl = $params['wsdl'];
              }
          }
      }
docs: Load WSDL from config
  
  Either a single WSDL location as string or a list of WSDL locations as array.
  
  @param array $params
  @return void