code: function getContacts($page_index = 1, $page_size = 100, $standard_fields = array(), $custom_fields = array())
      {
          $queryParameters = array(
              'page_index' => $page_index,
              'page_size' => $page_size,
              'standard_field' => $standard_fields
          );
  
          $queryParameters = $this->appendArrayFields($queryParameters, 'custom_field', $custom_fields);
  
          return $this->get('contacts', $queryParameters);
      }
docs: Returns a page of contacts in the account.
  
  @param number $page_index
  the index of the result page to fetch
  @param number $page_size
  the number of results to fetch per page
  @param string[] $standard_fields
  the standard fields to retrieve for the contacts
  @param string[] $custom_fields
  the custom fields to retrieve for the contacts
  @return \em com_maileon_api_MaileonAPIResult
  the result object of the API call, with a com_maileon_api_contacts_Contacts
  available at com_maileon_api_MaileonAPIResult::getResult()
  @throws com_maileon_api_MaileonAPIException
  if there was a connection problem or a server error occurred