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For 2023 (and 2024 ...) - we are now fully retired from IT training.
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Asyncronous call from Javascript on client to PHP on server
Web2 and caching example from a Well House Consultants training course
More on Web2 and caching [link]

This example is described in the following article(s):
   • Ajax - going Asyncronous and what it means - [link]

If you're searching for a page where you can view this page, select here

Source code: ajax456.html Module: H307
<html>
<head>
<title>AJAX in your web page</title>
<style>
#result { background-color: #DDDDFF;}
</style>
<script type=text/javascript language=javascript>
<!-- Hide Javascript on old browsers

var rqo;

function aboutlang(current) {
        var lang = current.options[current.selectedIndex].value;

        if (lang != "") {
        document.getElementById("result").innerHTML =
                "Fetching data ... <br /><br /><b>" + lang + "</b>";

        rqo = new XMLHttpRequest();
        var qs = encodeURIComponent(lang);
        var qry = "ajaxcode.php?towhich=" + qs;
        rqo.open('GET',qry,true);
        rqo.send(null);

        rqo.onreadystatechange = handlelang;

        }
        return false;

}

function handlelang() {
        document.getElementById("result").innerHTML =
                rqo.responseText + " (via Ajax)";

}
-->
</script>
</head>
<body>
<h1>Ajax demonstration - Asynchronous Javascript and XML</h1>
The selection box on this page calls up a server side program
(an application server / content provider / web service) and
displays elements of the result in the changeable area of the page
<hr />
<form>Please select a programming language
<select onChange="aboutlang(this)">
<option value="None">------</option>
<option value="Perl">Perl</option>
<option value="PHP">PHP</option>
<option value="Python">Python</option>
</select>
<input type="submit" value="Reload page / Reset"/>
</form>
<p id="result">This text initially loaded with page<br /><br />
<b>When you make a selection, the answer comes here</b></p>
<hr />
Ajax stands for "Asynchronous Javascript and XML" ... and this demonstration
uses it.<br /><br />

Using Ajax, a suitable browser can ask a server for dynamic information
to be filled in to an existing page, without the need to retransmit the
whole page - and in this example, we're calling up a server to replace the
text in the light blue box just above whenever a selection element on the
form is completed.<br /><br />

In this simple example too, we have not checked within our JavaScript as
to the make / version of the browser, so if it's used with a non
compliant browser it will fail silently.
</body>
</html>

Learn about this subject
This module and example are covered on our public PHP Techniques course. If you have a group of three or more trainees who need to learn the subject, we can also arrange a private or on site course for you.

Books covering this topic
Yes. We have over 700 books in our library. Books covering PHP are listed here and when you've selected a relevant book we'll link you on to Amazon to order.

Other Examples
This example comes from our "Web2 and caching" training module. You'll find a description of the topic and some other closely related examples on the "Web2 and caching" module index page.

Full description of the source code
You can learn more about this example on the training courses listed on this page, on which you'll be given a full set of training notes.

Many other training modules are available for download (for limited use) from our download centre under an Open Training Notes License.

Other resources
• Our Solutions centre provides a number of longer technical articles.
• Our Opentalk forum archive provides a question and answer centre.
The Horse's mouth provides a daily tip or thought.
• Further resources are available via the resources centre.
• All of these resources can be searched through through our search engine
• And there's a global index here.

Purpose of this website
This is a sample program, class demonstration or answer from a training course. It's main purpose is to provide an after-course service to customers who have attended our public private or on site courses, but the examples are made generally available under conditions described below.

Web site author
This web site is written and maintained by Well House Consultants.

Conditions of use
Past attendees on our training courses are welcome to use individual examples in the course of their programming, but must check the examples they use to ensure that they are suitable for their job. Remember that some of our examples show you how not to do things - check in your notes. Well House Consultants take no responsibility for the suitability of these example programs to customer's needs.

This program is copyright Well House Consultants Ltd. You are forbidden from using it for running your own training courses without our prior written permission. See our page on courseware provision for more details.

Any of our images within this code may NOT be reused on a public URL without our prior permission. For Bona Fide personal use, we will often grant you permission provided that you provide a link back. Commercial use on a website will incur a license fee for each image used - details on request.

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