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Concept visual
Start at both ends
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:
Customer info will be listed here...
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) {
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();
}
The showCustomer() function does the following: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 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
Formula
$mysqli = new mysqli("servername ", " username ", " password ", " dbname
");
if($mysqli->connect_error) {
exit('Could not connect');
}
$sql = "SELECT customerid, companyname, contactname, address, city, postalcode, countrycustomerid = ?";
$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>";?>