PHP - AJAX And MySQL

By Nirlipta Majumdar
10-01-2019
2172

PHP - AJAX and MySQL


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


Person info will be listed here...

Example Explained - The MySQL Database

The database table we use in the example above looks like this:

idFirstNameLastNameAgeHometownJob
1PeterGriffin41QuahogBrewery
2LoisGriffin40NewportPiano Teacher
3JosephSwanson39QuahogPolice Officer
4GlennQuagmire41QuahogPilot


Example Explained

In the example above, when a user selects a person in the dropdown list above, a function called "showUser()" is executed.

The function is triggered by the onchange event.

Here is the HTML code:

Example

<html>
<head>
<script>
function showUser(str) {
    if (str == "") {
        document.getElementById("txtHint").innerHTML = "";
        return;
    } else { 
        if(window.XMLHttpRequest) {
            // code for IE7+, Firefox, Chrome, Opera, Safari
            xmlhttp = newXMLHttpRequest();
        } else {
            // code for IE6, IE5
            xmlhttp = newActiveXObject("Microsoft.XMLHTTP");
        }
        xmlhttp.onreadystatechangefunction() {
            if(this.readyState == 4 && this.status == 200) {
                document.getElementById("txtHint").innerHTML = this.responseText;
            }
        };
        xmlhttp.open("GET","getuser.php?q="+str,true);
        xmlhttp.send();
    }
}
</script>
</head>
<body>

<form>
<select name="users"onchange="showUser(this.value)">
  <option value="">Select a person:</option>
  <option value="1">Peter Griffin</option>
  <option value="2">Lois Griffin</option>
  <option value="3">Joseph Swanson</option>
  <option value="4">Glenn Quagmire</option>
  </select>
</form>
<br>
<div id="txtHint"><b>Person info will be listed here...</b></div>

</body>
</html>
Run example »

Code explanation:

First, check if person is selected. If no person is selected (str == ""), clear the content of txtHint and exit the function. If a person is selected, do the following:

  • 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 PHP File

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

The source code in "getuser.php" runs a query against a MySQL database, andreturns the result in an HTML table:

<!DOCTYPE html>
<html>
<head>
<style>
table {
    width: 100%;
    border-collapse:collapse;
}

table, td, th {
    border: 1px solid black;
    padding: 5px;
}

th {text-align: left;}
</style>
</head>
<body>


$q = intval($_GET['q']);

$con = mysqli_connect('localhost','peter','abc123','my_db');
if (!$con) {
    die('Could not connect: ' . mysqli_error($con));
}

mysqli_select_db($con,"ajax_demo");
$sql="SELECT * FROM user WHERE id = '".$q."'";
$result = mysqli_query($con,$sql);

echo "






";
while($row = mysqli_fetch_array($result)) {
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
    echo "";
}
echo "
FirstnameLastnameAgeHometownJob
" . $row['FirstName'] . "" . $row['LastName'] . "" . $row['Age'] . "" . $row['Hometown'] . "" . $row['Job'] . "
"
;
mysqli_close($con);
?>

</body>
</html>

Explanation: When the query is sent from the JavaScript to the PHP file, the following happens:

  1. PHP opens a connection to a MySQL server
  2. The correct person is found
  3. An HTML table is created, filled with data, and sent back to the "txtHint" placeholder


Related Tutorials