AJAX Database Example

AJAX can be used for interactive communication with a database.

The following example will demonstrate how a web page can fetch information from a database with AJAX:

Example

<!DOCTYPE html>
<html>
<style>
th,td {
padding: 5px;
}
</style>
<body>

<h2>The XMLHttpRequest Object</h2>

<form action="">
<select name="customers" onchange="showCustomer(this.value)">
<option value="">Select a customer:</option>
<option value="ALFKI">Alfreds Futterkiste</option>
<option value="NORTS ">North/South</option>
<option value="WOLZA">Wolski Zajazd</option>
</select>
</form>
<br>
<div id="txtHint">Customer info will be listed here...</div>

<script>
function showCustomer(str) {
if (str == "") {
document.getElementById("txtHint").innerHTML = "";
return;
}
const xhttp = new XMLHttpRequest();
xhttp.onload = function() {
document.getElementById("txtHint").innerHTML = this.responseText;
}
xhttp.open("GET", "getcustomer.php?q="+str);
xhttp.send();
}
</script>
</body>
</html>

Try it now

Example Explained - The showCustomer() Function

When a user selects a customer in the dropdown list above, a function called showCustomer() is executed. The function is triggered by the onchange event:

showCustomer

The showCustomer() function does the following:

Check if a customer is selected
Create an XMLHttpRequest object
Create the function to be executed when the server response is ready
Send the request off to a file on the server
Notice that a parameter (q) is added to the URL (with the content of the dropdown list)

The AJAX Server Page

The page on the server called by the JavaScript above is a PHP file called "getcustomer.php".

The source code in "getcustomer.php" runs a query against a database, and returns the result in an HTML table:

<?php
$mysqli = new mysqli("servername", "username", "password", "dbname");
if($mysqli->connect_error) {
exit('Could not connect');
}

$sql = "SELECT customerid, companyname, contactname, address, city, postalcode, country
FROM customers WHERE customerid = ?";

$stmt = $mysqli->prepare($sql);
$stmt->bind_param("s", $_GET['q']);
$stmt->execute();
$stmt->store_result();
$stmt->bind_result($cid, $cname, $name, $adr, $city, $pcode, $country);
$stmt->fetch();
$stmt->close();

echo "<table>";
echo "<tr>";
echo "<th>CustomerID</th>";
echo "<td>" . $cid . "</td>";
echo "<th>CompanyName</th>";
echo "<td>" . $cname . "</td>";
echo "<th>ContactName</th>";
echo "<td>" . $name . "</td>";
echo "<th>Address</th>";
echo "<td>" . $adr . "</td>";
echo "<th>City</th>";
echo "<td>" . $city . "</td>";
echo "<th>PostalCode</th>";
echo "<td>" . $pcode . "</td>";
echo "<th>Country</th>";
echo "<td>" . $country . "</td>";
echo "</tr>";
echo "</table>";
?>

Practice Excercise Practice now

AJAX Database Example