AJAX Database Example
AJAX can be used for interactive communication with a database.
AJAX Database Example
The following example demonstrates how a web page can fetch information from a database using AJAX:
Example:
Select a customer:
Customer info will be listed here...
Example Explained - The showCustomer() Function
When a user selects a customer from the dropdown list above, a function called showCustomer() is executed. This function is triggered by the onchange event:
JavaScript Code:
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();}
Function Explanation:
- Check if a customer is selected. If not, clear the content of the txtHint placeholder and exit the function.
- Create an XMLHttpRequest object.
- Define the function to be executed when the server response is ready.
- Send the request to a file on the server, adding a parameter (q) 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 named "getcustomer.php".
The source code in "getcustomer.php" runs a query against a database and returns the result in an HTML table:
PHP Code:
<?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><th>CustomerID</th><td>" . $cid . "</td></tr>";
echo "<tr><th>CompanyName</th><td>" . $cname . "</td></tr>";
echo "<tr><th>ContactName</th><td>" . $name . "</td></tr>";
echo "<tr><th>Address</th><td>" . $adr . "</td></tr>";
echo "<tr><th>City</th><td>" . $city . "</td></tr>";
echo "<tr><th>PostalCode</th><td>" . $pcode . "</td></tr>";
echo "<tr><th>Country</th><td>" . $country . "</td></tr>";
echo "</table>";
?>
This code provides a real-time way to fetch and display customer information from a database based on user input, making the application more interactive and responsive.
