vBulletin LTS

Intergrating AJAX Technology Into Your Modifications

by Zero Tolerance 31 Jul 2005

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This How-To will show you how to use the defined AJAX functions within vBulletin so developers can see how easily it is to intergrate AJAX technology into modifictions. Please note this tutorial is aimed at developers with some javascript knowledge.

Step 1 - Understand AJAX:

As many of you will know, AJAX gives the ability to pass data through a stream and recieve any data returned with no reloading, so if you're thinking of intergrating AJAX then you must first have a scenario where you wish to push data and recieve it, recieval is not required however is probably the best part of AJAX in a users opinion due to the dynamic changes that occur to present the recieved data.

Step 2 - Setting Up AJAX:

Okay, so you want to set up AJAX, real easy, the first step is to create an AJAX Object, this can be done with ease using the vBulletin set-up, an example is below:

Code:

My_AJAX_Object = new vB_AJAX_Handler(true);

You'll notice the one and only passive variable here for the function 'vB_AJAX_Handler' is set to 'true', this determines wether to use asynchronous or not, set to false if you do not desire to use it, if you're unsure leave this set to true.

So now you have your AJAX Object set up, before firing data you'll need to to set the object to respond to a function for when it recieves data, an example is below:

Code:

My_AJAX_Object.onreadystatechange(My_AJAX_Reciever);

Here the parameter is not so much a variable, but infact a function name, in this case i put 'My_AJAX_Reciever', so that function must exist, an example function is below:

Code:

function My_AJAX_Reciever()
{
	if (My_AJAX_Object.handler.readyState == 4 && My_AJAX_Object.handler.status == 200 && My_AJAX_Object.handler.responseText)
	{
		alert('Data recieved successfully\n\n' + My_AJAX_Object.handler.responseText)
	}
}

This function pretty much checks the stream has loaded and sent data back to the browser, upon success it will alert you to say it was successful, and the data it recieved. How you handle the data is upto you.

Step 3 - Firing And Recieving Data:

So now you want to fire some data through AJAX, and get some back, let's first look how we fire data:

Code:

My_AJAX_Object.send('myfile.php', 'do=ajax&pagevar=text');

Let's take a quick overlook at the parameters used here:

Parameter 1 - The file you want to send the data to.
Parameter 2 - Post variables you want to send through.

In most cases your post variables (parameter 2) would fluxuate, and you may want to send some variables that users have inputted, if so you may want to take advantage of vBulletin's javascript emulation of urlencode(), first off you'd parse the variable in javascript before firing off, as shown below:

Code:

My_Variable = PHP.urlencode(My_Variable);

This makes the variable safe for the stream to send the data, however some characters will be broken, to fix these in your php when collecting the variable you would parse it like so:

PHP Code:


$My_Variable = convert_urlencoded_unicode($My_Variable);

Okay, so you've now fired data off to 'myfile.php', with the variables: do (ajax) and pagevar (text). Now comes the PHP part, where you handle the data and output some back to be recieved:

PHP Code:


if ($_POST['do'] == 'ajax')

{

    echo $_POST['pagevar'];

    exit;

}

Simple as that? Pretty much, ofcourse the desired data to be sent back due to the data sent is completely up to you, if you've set the javascript up with the examples used above you should get a message saying:

Data recieved successfully

text

So if you're not sure, what the PHP outputs AJAX grabs, and just to ensure the script ends there it's best to make PHP stop execution of any code underneath by using exit;, this ofcourse it not required, just likely in most situations

Remember, to grab using AJAX what PHP outputted, the code is My_AJAX_Object.responseText

Final Line - Handling Data and Dynamics:

So you've managed to successfully fire some data off, and got some back, now you want to fiddle with it in Javascript and make changes to your page?
Then i'm afraid you're on your own for that job, how you handle the recieved data is completely upto you and the scenario you're using AJAX in.

If you wish to see more information on AJAX, i suggest you look at this tutorial i wrote a while ago for vBulletin.org, it includes more information on AJAX than posted here

[Tutorial] Developers Introduction To AJAX Technology

Any questions/problems reply here and i'll try to resolve them for you, the code above is all written off the top of my head, but i don't see any errors myself, feel free to report them to me though

- Zero Tolerance

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