// in a js "class"

this.ajaxError=function(response)
{
  alert('AJAX error!'+response)
}

this.ajax=function(url,type,success,error)
{
   $.ajax({
                     url: url,
                     type:type,
                     success: success,
                     error: error
          });
}

this.showMessage=function(response)
{
  alert(JSON.parse(response));
}

this.open=function()
{
  alert("1");
  this.ajax('/message/open/173','text',this.showMessage,this.ajaxError);
}


//php in vew/open.ctp
<?php
?>


//messagecontroller.php

public function open($stream_id)
{
  /*$result = $this->Stream->find('first', array(
        'conditions' => array('Stream.id' => $stream_id
        )
       ));
  echo json_encode($result);*/
  echo "id:".$stream_id;
}