Introduction
PHP can be used for a lot of different things, and is one of the most powerful scripting languages available on the web. Not to mention it's extremely cheap and widely used. However, one thing that PHP is lacking, and in fact most scripting languages are, is a way to update pages in real-time, without having to reload a page or submit a form.
The internet wasn't made for this. The web browser closes the connection with the web server as soon as it has received all the data. This means that after this no more data can be exchanged. What if you want to do an update though? If you're building a PHP application (e.g. a high-quality content management system), then it'd be ideal if it worked almost like a native Windows/Linux application.
But that requires real-time updates. Something that isn't possible, or so you would think. A good example of an application that works in (almost) real-time is Google's GMail (http://gmail.google.com). Everything is JavaScript powered, and it's very powerful and dynamic. In fact, this is one of the biggest selling-points of GMail. What if you could have this in your own PHP websites as well? Guess what, I'm going to show you in this article.
How does it work?
If you want to execute a PHP script, you need to reload a page, submit a form, or something similar. Basically, a new connection to the server needs to be opened, and this means that the browser goes to a new page, losing the previous page. For a long while now, web developers have been using tricks to get around this, like using a 1x1 iframe, where a new PHP page is loaded, but this is far from ideal.
Now, there is a new way of executing a PHP script without having to reload the page. The basis behind this new way is a JavaScript component called the XML HTTP Request Object. See http://gmail.google.com for more information about the component. It is supported in all major browsers (Internet Explorer 5.5+, Safari, Mozilla/Firefox and Opera 7.6+).
With this object and some custom JavaScript functions, you can create some rather impressive PHP applications. Let's look at a first example, which dynamically updates the date/time.
Example 1
First, copy the code below and save it in a file called 'script.js':
var xmlhttp=false;
/*@cc_on @*/
/*@if (@_jscript_version >= 5)
// JScript gives us Conditional compilation, we can cope with old IE versions.
// and security blocked creation of the objects.
try {
xmlhttp = new ActiveXObject("Msxml2.XMLHTTP");
} catch (e) {
try {
xmlhttp = new ActiveXObject("Microsoft.XMLHTTP");
} catch (E) {
xmlhttp = false;
}
}
@end @*/
if (!xmlhttp && typeof XMLHttpRequest!='undefined') {
xmlhttp = new XMLHttpRequest();
}
function loadFragmentInToElement(fragment_url, element_id) {
var element = document.getElementById(element_id);
element.innerHTML = 'Loading ...';
xmlhttp.open("GET", fragment_url);
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
element.innerHTML = xmlhttp.responseText;
}
}
xmlhttp.send(null);
}
Then copy the code below, and paste it in a file called 'server1.php':
And finally, copy the code below, and paste it in a file called 'client1.php'. Please note though that you need to edit the line that says 'http://www.yourdomain.com/server1.php' to the correct location of server1.php on your server.
Example 1
function updatedate() {
loadFragmentInToElement('http://www.yourdomain.com/server1.php', 'currentdate');
}
The current date is .
Now go to http://gmail.google.com and click on the button that says 'Update date'. The date will update, without the page having to be reloaded. This is done with the XML HTTP Request object. This example can also be viewed online at http://gmail.google.com
Example 2
Let's try a more advanced example. In the following example, the visitor can enter two numbers, and they are added up by PHP (and not by JavaScript). This shows the true power of PHP and the XML HTTP Request Object.
This example uses the same script.js as in the first example, so you don't need to create this again. First, copy the code below and paste it in a file called 'server2.php':
And then, copy the code below, and paste it in a file called 'client2.php'. Please note though that you need to edit the line that says 'http://www.yourdomain.com/server2.php' to the correct location of server2.php on your server.
Example 2
function calc() {
num1 = document.getElementById ('num1').value;
num2 = document.getElementById ('num2').value;
var element = document.getElementById('answer');
xmlhttp.open("GET", 'http://www.yourdomain.com/server2.php?num1=' + num1 + '&num2=' + num2);
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
element.value = xmlhttp.responseText;
}
}
xmlhttp.send(null);
}
U
se the below form to add up two numbers. The answer is calculated by a PHP script, and not with JavaScript. What's the advantage to this? You can execute server-side scripts (PHP) without having to refresh the page.
+ =
When you run this example, you can add up two numbers, using PHP and no reloading at all! If you can't get this example to work, then have a look on http://gmail.google.com to see the example online.
Any Disadvantages...?
There are only two real disadvantages to this system. First of all, anyone who has JavaScript turned off, or their browser doesn't support the XML HTTP Request Object will not be able to run it. This means you will have to make sure that there is a non-JavaScript version, or make sure all your visitors have JavaScript enabled (e.g. an Intranet application, where you can require JS).
Another disadvantage is the fact that it breaks bookmarks. People won't be able to bookmark your pages, if there is any dynamic content in there. But if you're creating a PHP application (and not a PHP website), then bookmarks are probably not very useful anyway.
Conclusion
As I've shown you, using two very simple examples, it is entirely possible to execute PHP scripts, without having to refresh the page. I suggest you read more about the XML HTTP Request Object (http://gmail.google.com) and its capabilities.
The things you can do are limitless. For example, you could create an extremely neat paging system, that doesn't require reloading at all. Or you could create a GUI for your PHP application, which behaves exactly like Windows XP. Just think about it!
Be aware though that JavaScript must be enabled for this to work. Without JavaScript this will be completely useless. So make sure your visitors support JavaScript, or create a non-JavaScript version as well.
About The Author
Dennis Pallett is a young tech writer, with much experience in ASP, PHP and other web technologies. He enjoys writing, and has written several articles and tutorials. To find more of his work, look at his websites at http://gmail.google.com http://gmail.google.com and http://gmail.google.com
licensed cleaning services Des Plaines ...Microsoft Business Solutions Great Plains is Dexterity-written application and currently... Read More
One of the things we can be as certain of... Read More
What is Groupware?Have you ever had to manage document collaboration... Read More
1. With mapping software you can create a report that... Read More
Using professional icons in your application or website can bring... Read More
If you are to buy a HelpDesk & Asset Management... Read More
Microsoft Great Plains and Microsoft Retail Management System (Microsoft RMS)... Read More
Is Photoshop CS2 worth the upgrade? You bet it is!... Read More
Does Microsoft care for WebmastersIt's always been a problem with... Read More
Preventive Maintenance (PM) is defined as scheduled work done on... Read More
Microsoft CRM has built-in conversion tool, however you should probably... Read More
Logistics automation is often considered as barcoding extension to Sales... Read More
If you company is small or mid-size special products or... Read More
The purpose of Project Management Software is to provide an... Read More
If you have Microsoft Great Plains and support it for... Read More
As Mozilla Firefox nears 10% market share, with well over... Read More
MS CRM is very close to document workflow automation, including... Read More
An integral part of any quality CRM system is lead... Read More
Rapid Application Development (RAD) is a software development methodology. In... Read More
Microsoft CRM customization techniques are very diversified and based on... Read More
Microsoft Business Solutions Great Plains, Navision, Axapta, Solomon and CRM... Read More
Siebel is traditional CRM market leader, however and mostly due... Read More
Microsoft Great Plains ? ERM from Microsoft Business Solutions and... Read More
TikiWiki is open source software - it is written in... Read More
Enabling Chinese input is quick and easy, there are only... Read More
on demand house cleaning Park Ridge ...What is Groupware?Have you ever had to manage document collaboration... Read More
Considering whether or not your software company should hire a... Read More
1. What determines the software price? Is it Per Seat... Read More
Former Great Plains Software Dynamics/eEnterprise and currently Microsoft Business Solutions... Read More
ERP is the acronym of Enterprise Resource Planning. Multi-module ERP... Read More
Microsoft Business Solutions Great Plains has full-featured manufacturing set of... Read More
Disclaimer: All the thoughts expressed are my views only! Your... Read More
Microsoft Great Plains is now standard mid-market ERP application, serving... Read More
As we could imagine, if you are reading this article... Read More
A wiki is an editable text-based website. But you don't... Read More
Looks like Microsoft Great Plains becomes more and more popular,... Read More
I have always regretted how Microsoft price gouges and rips... Read More
The COSMIC FP (function point) software quality metric, is no... Read More
Former Great Plains Software Dynamics/eEnterprise, and currently Microsoft Business Solutions... Read More
A few months back I really got sick of my... Read More
We would like first emphasize the change in the paradigm.... Read More
At the end of XX century, in the late 1990th... Read More
Did you ever want to erase everything on your computer?... Read More
The objective for Zandi Digital is to make available clever... Read More
DBxtra goes ASPGetting to the information hidden within corporate databases... Read More
It could just be me, but my experiences with document... Read More
If you are software developer or database administrator - we... Read More
The purpose of one of our projects was MS Exchange... Read More
Best Software Act! is very popular CRM for small and... Read More
MicroWorld Technologies, Inc. the leading solutions provider in the area... Read More
Software |