3 min read
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:
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()
onchange
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:
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>"; ?>
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