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Ajax with jQuery
Let's implement this very simple Ajax example:
jQuery
First you'll need to include the latest stable version of jQuery. You can either:
- Point straight to the version hosted on the official website (quick and easy, but performance issues).
- Download the library, upload it to your website via FTP, and point to your local file.
In both cases, the syntax is the same:
<script src="path/to/the/file/jquery-3.1.0.min.js"></script>
In this example we'll keep things simple and point to the hosted version:
<script src="https://code.jquery.com/jquery-3.1.0.min.js"></script>
Client-side
First, let's have a look at the webpage itself:
<html>
<head>
<title>Ajax example</title>
<script src="https://code.jquery.com/jquery-3.1.0.min.js"></script>
<script>
function DoDearch()
{
// This is the Ajax call to "getdata.php"
$.ajax({
method: "GET",
url: "getdata.php",
data: { searchValue: $('#searchValue').val() }
})
// And this handles the response
.done(function( response ) {
// Write response to our "results" element
$( "#results" ).html(response);
});
}
</script>
</head>
<body>
<h1>Ajax example</h1>
Enter value: <input type="text" id="searchValue">
<input type="button" value="Search" onclick="DoDearch();">
<p id="results"></p>
</body>
</html>
The HTML is fairly simple. Note the text box, button, and blank paragraph to display the results later on.
The bit of interest is the Ajax jQuery call, here:
// This is the Ajax call to "getdata.php"
$.ajax({
method: "GET",
url: "getdata.php",
data: { searchValue: $('#searchValue').val() }
})
In the call we specify 3 things:
- We want to use the GET HTTP protocol (it works fine with POST too!)
- We want to call a file called "getdata.php". Obviously you need to create this file (see below).
- We pass ONE parameter to the PHP file: the value typed in the search box.
Once the response comes back from the server, this bit of code decides what to do:
// And this handles the response
.done(function( response ) {
// Write response to our "results" element
$( "#results" ).html(response);
});
In this case, we simply display the result ("response" variable) in our blank paragraph element ("results").
Server-side
The server-side script is for you to complete:
<?php // Retreive value passed from Ajax call $searchValue = $_GET['searchValue']; // Debug message echo "Performing search for ".$searchValue."..."; // Connect to database // Build SQL statement // Run SQL statement // Loop through results and display ?>
The only thing of interest is this line:
$searchValue = $_GET['searchValue'];
It simply reads the search value passed from the Ajax call. If you use the POST protocol instead of GET in your Ajax call, then replace $_GET by $_POST!
Once you have obtained the value, simply perform a database search, as covered in an earlier week.
More
Please see official documentation for more information!
