XML : no results when using json.api but getting results using xml.api in waveframework

I am using php waveframework and when I look at the results from:
http://localhost/json.api?www-command=class-methode
I get an empty page,
but when I use:
http://localhost/xml.api?www-command=class-methode
I see the espected results.

I thought that the framework gave both the results?
I can not find the difference in the help files.

If I use the
&www-return-type=json
it still gives me an empty page, but it gives me the right result when I
use: &www-return-type=xml

Is there a variable that needs to be set?

The client who will be using the service needs the results in json format.

This is the model:
public function alle_landen(){

      $rows = array();      $Aantal = 0;        $connect = odbc_connect($this->dsn_Name, $this->dsn_UserName, $this->dsn_Pass);        # query the table      $query = "SELECT CDLAND, OMSCHR FROM LAND";          # perform the query      $result = odbc_exec($connect, $query);        # fetch the data from the database            while($myRow = odbc_fetch_array( $result )){              $Aantal += 1;              $rows[] = $myRow;      }        # close the connection      odbc_close($connect);        if($rows){          // Returning entries and the total row count          return array('entries'=>$rows,'total'=>$Aantal);      } else {          // Returning empty data          return array('entries'=>array(),'total'=>0);      }    }    

and this is the controller:

public function allelanden(){

      // Loading the model and data to the model            $data = $this->getModel('landen');      $data = $data->alle_landen();          if($data){          return $this->resultTrue('Request complete', $data);      } else {          return $this->resultFalse('Search failed');      }      }    

Thanks in advance,
Brian