如何从jqgrid中的postdata获取值

Question

how to use data in postdata in jqgrid? below is my code. the value asset_id is there when I alert it, but how to get the value in PHP?

edittype:"select",
width: 200,
editoptions: {
maxlength:30,
dataUrl : "/build/15",
postData: function (rowid) {
  return {
    // action: "getState",
    asset_id: $(this).jqGrid("getCell", rowid, "asset_id")
  };
},

this is in my PHP code.

function build($program){

    $data = $this->input->post("asset_id"); // i get object error


    // I try to echo the value of post data in here, but I get object error.
}

i try to put the value in postdata in my controller.