jQuery Grid Plugin - jqGrid

By following the tutorial on master detail grid, I able to make it run perfectly.

However, when I want to combine this existing master detail with the text box +search button function, it is not working. No error is shown. In this case, how to debug?

Codes I add in to the existing master detail 's html page:

var timeoutHnd;
var flAuto = false;

function doSearch(ev){...}
function gridReload(){...}
function enableAutosubmit(state){...}

var nm_mask = jQuery("#item_nm").val();

var cd_mask = jQuery("#search_cd").val();
alert(nm_mask); alert(cd_mask);

Whenever I click search button, red bar will load, the grid will refresh, but data not changing at all.

When I debug the js code, it shows the value as expected.

If I add in this line, then both the master and detail grid will be blank--> mtype: "POST",

I'm not sure which part is facing problem.
How to debug?
when I click on the search button in html page, it will call the master grid php page, pass in parameter.
I have no idea what is whole data that passed in, and returned from php page.

If I directly open up master grid php page, then I have no way to trace what is missing on the road. I have to open up the html page to call to the master grid php page...

Tony, any way to trace? Any idea on what's missing?