Server Side Paging with jqxGrid using PHP and MySQL

This help topic shows how to implement server-side paging with the jqxGrid widget. The Grid will request data from the server when the user navigates to a new page or changes the page's size. The server-side script is going to deliver the data records in JSON format depending on the page number and page size. We will obtain the data from Northwind Database and especially from the Orders table. You can download the Northwind database .sql script here and run it into MySQL to create the database. You can download the Northwind database .sql script here and run it into MySQL to create the database.
By default, the Grid sends the following data to the server:

Assume that you are working on a web page which lists the customers from a database. Assume that you need to display 10 records in a page. The database has 30,000 records consisting all the customers. In the above scenario, it really makes sense to retrieve only the required records. for example, in the first page, retrieve 1 to 10 records. When the user clicks on “next” button, retrieve records 11 to 20 and so on. In this help topic, we will show you how to populate the jqxGrid on demand when the current page is changed. When a page is changed, the jqxGrid will request records in a specific range from the server. In reply to each request for information that the Grid plug-in makes to the server, it expects to get a well formed JSON object. Let’s see how to achieve that in a few steps.

1. The first step is to create the file we’ll connect with. We will call the file ‘connect.php’ 
<?php
# FileName="connect.php"
$hostname = "localhost";
$database = "northwind";
$username = "root";
$password = "";
?>
2. The second step is to create the file that will handle the queries. We will call the file data.php. The data.php file connects to the ‘Customers’ table from the Northwind Database and returns the data as JSON. Our goal is to send data to client in small pieces that the client requests, and respond when the page number or page size is changed by the user. In the implementation, we check for the ‘pagenum’ and ‘pagesize’ members which the Grid sends to the server and we use the values of these members to specify the range of records in the query to the database. We also make a query to find the total rows in the ‘Customers’ table. The returned JSON data contains two thinkgs- the total rows in the ‘Customers’ table and the requested records. 
<?php
	#Include the connect.php file
include ('connect.php');
// Connect to the database
$mysqli = new mysqli($hostname, $username, $password, $database);
/* check connection */
if (mysqli_connect_errno())
	{
	printf("Connect failed: %s\n", mysqli_connect_error());
	exit();
	}
// get data and store in a json array
$pagenum = $_GET['pagenum'];
$pagesize = $_GET['pagesize'];
$start = $pagenum * $pagesize;
$query = "SELECT SQL_CALC_FOUND_ROWS CompanyName, ContactName, ContactTitle, Address, City, Country FROM customers LIMIT ?,?";
$result = $mysqli->prepare($query);
$result->bind_param('ii', $start, $pagesize);
$result->execute();
/* bind result variables */
$result->bind_result($CompanyName, $ContactName, $ContactTitle, $Address, $City, $Country);
/* fetch values */
while ($result->fetch())
	{
	$customers[] = array(
		'CompanyName' => $CompanyName,
		'ContactName' => $ContactName,
		'ContactTitle' => $ContactTitle,
		'Address' => $Address,
		'City' => $City,
		'Country' => $Country
	);
	}
$result = $mysqli->prepare("SELECT FOUND_ROWS()");
$result->execute();
$result->bind_result($total_rows);
$result->fetch();
$data[] = array(
	'TotalRows' => $total_rows,
	'Rows' => $customers
);
echo json_encode($data);
/* close statement */
$result->close();
/* close connection */
$mysqli->close();
?>
3. The final step is to create the Grid and bind it to the ‘Customers’ table. Our goal is to populate the Grid on demand when a page or the page’s size is changed.
Here’s the full source code: 
<!DOCTYPE html>
<html lang="en">
<head>
    <link rel="stylesheet" href="../jqwidgets/styles/jqx.base.css" type="text/css" />
    <link rel="stylesheet" href="../jqwidgets/styles/jqx.classic.css" type="text/css" />
    <meta name="viewport" content="width=device-width, initial-scale=1">
    <script type="text/javascript" src="../jquery-1.11.1.min.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxcore.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxbuttons.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxscrollbar.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxmenu.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxcheckbox.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxlistbox.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxdropdownlist.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxgrid.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxgrid.pager.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxgrid.selection.js"></script>
    <script type="text/javascript" src="../jqwidgets/jqxdata.js"></script>
    <script type="text/javascript">
        $(document).ready(function () {
            // prepare the data
            var theme = 'classic';
            var source =
            {
                datatype: "json",
                datafields: [
					 { name: 'CompanyName' },
					 { name: 'ContactName' },
					 { name: 'ContactTitle' },
					 { name: 'Address' },
					 { name: 'City' },
					 { name: 'Country' }
                ],
                cache: false,
                url: 'data.php',
                root: 'Rows',
                beforeprocessing: function (data) {
                    source.totalrecords = data[0].TotalRows;
                }
            };
            var dataadapter = new $.jqx.dataAdapter(source);
            // initialize jqxGrid
            $("#jqxgrid").jqxGrid(
            {
                width: 600,
                source: dataadapter,
                theme: theme,
                autoheight: true,
                pageable: true,
                virtualmode: true,
                rendergridrows: function (params) {
                    return params.data;
                },
                columns:
                [
                    { text: 'Company Name', datafield: 'CompanyName', width: 250 },
                    { text: 'Contact Name', datafield: 'ContactName', width: 200 },
                    { text: 'Contact Title', datafield: 'ContactTitle', width: 200 },
                    { text: 'Address', datafield: 'Address', width: 180 },
                    { text: 'City', datafield: 'City', width: 100 },
                    { text: 'Country', datafield: 'Country', width: 140 }
                ]
            });
        });
    </script>
<script async src="https://www.googletagmanager.com/gtag/js?id=G-2FX5PV9DNT"></script><script>window.dataLayer = window.dataLayer || [];function gtag(){dataLayer.push(arguments);}gtag('js', new Date());gtag('config', 'G-2FX5PV9DNT');</script></head>
<body class='default'>
    <div id="jqxgrid"></div>
</body>
</html>
Let’s see how the above code works. As we need to populate the Grid on demand, we set its ‘virtualmode’ property to true. This means that the Grid will display only the records returned as array from the ‘rendergridrows’ callback function. The Grid will make requests to the server when the user clicks the ‘Next’ or ‘Previous’ buttons or changes the page’s size. We also set the source object’s totalrecords property to the TotalRows value returned from the server. In the source object’s initialization we set the ‘datatype’ to ‘json’ as the returned data will be JSON data and the ‘root’ member to ‘Rows’ as the records are stored in the ‘Rows’ array.