jQuery Grid Plugin - jqGrid

I am trying to have a jqgrid on my webpage with all the functionality.

Currently I am able to fill the grid with data from mysql database.

Now I have kept add:true in the navgrid option and with the '+' icon it opens

a add dialog box with 3 fields which on submit I need to add to mysql database.

Here's my jqgrid code:

<script type="text/javascript">
jQuery(document).ready(function(){
$("#grid").jqGrid({ 
   // data: mydata, 
    datatype: 'json',
    mtype: 'POST',
    url: 'showResources.php',
    width: 700, 
    colNames:["LAB NAME","RESOURCE NAME","DESCRIPTION"], 
    colModel:[
    {name:'lab_name', index:'lab_name', width:40,editable:true, edittype: 'select', 
editoptions:{value:"nccs:NCCS;tcs:TCS;iisc:IISC;icgeb:ICGEB", 
dataInit:function(elem) 
        {
                $(elem).width('auto');
        }
}},
    {name:'resource_name', index:'resource_name', width:50,editable:true, 
editoptions:{size:'auto'}},
    {name:'description', index:'description', width:100,editable:true, 
edittype: 'textarea', editoptions:{rows:"2",cols:"20"}},
    ], 
    pager: "#pager", 
    rowNum:10, 
    rownumbers: true,
    rowList:[10,20,30],
    gridview: true,
    sortname: 'id', 
    viewrecords: true,
    loadonce: true,
    sortorder: "desc", 
    caption:"Resources",
    height: 250,
    editurl: 'addResource.php'      
    }).navGrid('#pager',{edit:false,add:true,del:false,search:true},{width: '330', 
closeAfterAdd: true });  
});
</script>

Here url:showResource.php is the page where I have the logic to fetch 
data into grid from mysql, and editurl: 'addResource.php' is where my 
 logic for adding the row is which is:
code:

$lab_name = $_POST['lab_name'];  //lab_name field from POST above
    $resource_name = $_POST['resource_name']; //resource_name field from POST above
    $description = $_POST['description'];  //description field from POST above
    $tb_name = 'tb_systb_resources';

    $add_query = "INSERT INTO $tb_name ('','lab_name','resource_name','description') 
VALUES ('',$lab_name,$resource_name,$description)";
    $result = mysql_query($add_query);
    if($result)
    {
        echo("<br>Input data is succeed");
    } 
    else
    {
        echo("<br>Input data is fail");
    }


Now when the page is loaded it says
Notice: Undefined index: lab_name in /opt/lampp/htdocs/hemang/addResource.php on line 10
Notice: Undefined index: resource_name in /opt/lampp/htdocs/hemang/addResource.php on line 11
Notice: Undefined index: description in /opt/lampp/htdocs/hemang/addResource.php on line 12
which i have printed and the grid is filled, and the data does add  from the 
dialog but does not store to db. So when I refresh the page or  grid it disappears. 
I am not sure of how to pass the 3 fields' values  from the submit button in add dialog box.
Please help.