EditableGrid how to fetch rows from MySql in php

I am trying to do an editable grid table in order to modify directly.
There is a field which I need to list all of it content so that I can select one.
Look at my code :

   

 function fetch_pairs($mysqli,$query){
    	if (!($res = $mysqli->query($query)))return FALSE;
    	$rows = array();
    	while ($row = $res->fetch_assoc()) {
    		$first = true;
    		$key = $value = null;
    		foreach ($row as $val) {
    			if ($first) { $key = $val; $first = false; }
    			else { $value = $val; break; } 
    		}
    		$rows[$key] = $value;
    	}
    	return $rows;
    }
    $grid->addColumn('product-name', 'Product', 'string' , fetch_pairs($mysqli,'SELECT name FROM table_product'),true); 

Select allOpen in new window

In my database I have two tables:

-table_add{id,product-name}
-table_product{id,name}

 But the list is not appearing.
I am getting this error:

Could not load JSON from url 'loaddata.php?db_tablename=table_add'

Any idea why ?