Maybe your problem is related to json because you return a bad json.

The correct formatted json that you return should be like this:

{"rows":[{"cell":[
"CSBM ","Query","2009","A"
]},
{"cell":[
"FSB ","Query","",""
]}]}.


Ps: sorry for my bad english.

Code snippet for grid:-

// Create the jqGrid instance
$grid = new jqGridRender($conn);
// Write the SQL Query
// We suppose that mytable exists in your database
$grid->SelectCommand = "select uid,lastname,firstname,phonehome,phonework,mobile from students ".$where;

// set the ouput format to json
$grid->dataType = 'json';
// Let the grid create the model
$grid->setColModel();
// Set the url from where we obtain the data
$grid->setUrl('students/getstudents.php');
// Set grid caption using the option caption
$grid->setGridOptions(array(
    "caption"=>"Students and their Courses",
    "rowNum"=>16,
    "sortname"=>"lastname",
    "rowList"=>array(16,30,50),
    "height"=>354,
    "width"=>900
    ));

$grid->addCol(array("name"=>"act"),"first");

// Change some property of the field(s)
$grid->setColProperty("uid", array("label"=>"ID", "width"=>20, "hidden"=>true));
$grid->setColProperty("act", array("label"=>"Actions", "width"=>90));
$grid->setColProperty("lastname", array("label"=>"Last Name", "width"=>200));
$grid->setColProperty("firstname", array("label"=>"First Name", "width"=>150));
$grid->setColProperty("phonehome", array("label"=>"Phone Home", "width"=>150));
$grid->setColProperty("phonework", array("label"=>"Phone Work", "width"=>150));
$grid->setColProperty("mobile", array("label"=>"Mobile", "width"=>150));

$grid->setSubGrid("students/getcourses.php",
        array('Course','Status','Year','Semester'),
        array(300,150,40,50),
        array('left','left','right','center'));

Code for subgid

require_once '../includes/jquery/jq-config.php';
// include the jqGrid Class
require_once "../includes/jquery/php/jqGrid.php";
// include the PDO driver class
require_once "../includes/jquery/php/jqGridPdo.php";
// Connection to the server
$conn = new PDO(DB_DSN,DB_USER,DB_PASSWORD);

// Get the needed parameters passed from the main grid
$rowid = jqGridUtils::Strip($_REQUEST["id"]);
if(!$rowid) die("Missed parameters");

// Create the jqGrid instance
$grid = new jqGrid($conn);
// Write the SQL Query
$grid->SubgridCommand = "select courses.course, studcourse.status, courses.year, courses.semester from studcourse, courses where studcourse.studentno =".$rowid." and studcourse.courseno = courses.uid";

// set the ouput format to json
$grid->dataType = 'json';
// Use the build in function for the simple subgrid
$grid->querySubGrid(array(&$rowid));
$conn = null; 

json returned by subgrid code

{"rows":[{"course":"CSBM ","status":"Query","year":"2009","semester":"A"},

{"course":"FSB ","status":"Query","year":"","semester":""}]}

Can someone please tell me why these records are not being displayed in the subgrid.