jQuery Grid Plugin - jqGrid

I've the last one release of jqGrid.

I want this features:

it have to load only once all the data and never ask it again to load again.

I'm using Yii framework so I don't have to do querys to SQL to load datas.

This is my example. I've an object $category.

In $category->elements i've all my elements.

So the count of element will be $count = count($category->elements) and so on.

When I have to iterete I will do

for ( $i = 0; $i < $count; $i++ ) {

$response[$i]['id'] = $category->elements[$i]->elementId

$response[$i]['cell'] = array( $category->elements[$i]->elementId,  $category->elements[$i]->title)

}

echo json_encode($response);

But it doesn't work ( nothing is loaded and the grid is "strange" )

Someone can gimme a simple example that fix my request and my code?