AJAX Database Example
AJAX can be used for interactive communication with a database.
AJAX Database Example
The following example will demonstrate how a web page can fetch information from a database with AJAX:
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
function showCustomer(str) {
var xhttp;
if (str == "") {
document.getElementById("txtHint").innerHTML = "";
return;
}
xhttp = new XMLHttpRequest();
xhttp.onreadystatechange = function() {
if (this.readyState
== 4 && this.status == 200) {
document.getElementById("txtHint").innerHTML
= this.responseText;
}
};
xhttp.open("GET",
"getcustomer.php?q="+str, true);
xhttp.send();
}
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 an 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>";
?>
