When you append the content to the end of your "curl" variable like you are, you are attempting to add it to be retrieved through a GET variable and will get a result in a request like http://localhost:8080/test/grab/http://stackoverflow.com/questions/ask. Clearly this is an invalid request. Your GET variable parsing is not going to be consistent and a dangerous way of passing data back to your controller (especially if users will be able to edit the appended value).
Instead, you should use the data attribute in jQuery to pass this information back in your POST request as described in the instructions here: http://api.jquery.com/jQuery.ajax/
On the Cake side, you'll be able to receive this value as $this->data['IDValueYouConfigured']. For example, if your AJAX request was like:
var whatContent=$("#testing").val();
var curl="http://localhost:8080/test/grab/";
$.ajax({
type: "POST",
url: curl,
data: "formValue="+whatContent,
success: function(data) {
alert(data);}
});
where formValue is the IDValueYouConfigured that I mentioned earlier.
More importantly, you seem to be misunderstanding proper use of the Cake framework and could be performing all of these functions MUCH more simply using things like the JsHelper, FormHelper, etc. I would recommend using the most RECENT version of Cake (1.3.3) and follow through the Blog tutorial at least once. This will lead to better questions which will be more likely to get helpful answers. Hope this helps.