In the AJAX example below we will demonstrate an RSS reader where the content from the RSS is loaded into the webpage without refreshing.RS...
In the AJAX example below we will demonstrate an RSS reader where the content
from the RSS is loaded into the webpage without refreshing.RSS Feed will be listed her
This example consists of three pages:
The form works like this:
The showRSS() Function
Every time an option is selected in the input field this function executes the following:
This example consists of three pages:
- a simple HTML form
- a JavaScript
- a PHP page.
The HTML Form
This is the HTML page. It contains a simple HTML form and a link to a JavaScript:<html> <head> <script type="text/javascript" src="getrss.js"></script> </head> <body> <form> Select an RSS-Feed: <select onchange="showRSS(this.value)"> <option value="Google">Google News</option> <option value="MSNBC">MSNBC News</option> </select> </form> <p><div id="rssOutput"> <b>RSS Feed will be listed here.</b></div></p> </body> </html> |
Example Explained - The HTML Form
As you can see, the HTML page above contains a simple HTML form with a drop-down box.The form works like this:
- An event is triggered when the user selects an option in the drop down box
- When the event is triggered, a function called showRSS() is executed.
- Below the form is a <div> called "rssOutput". This is used as a placeholder for the return data of the showRSS() function.
The JavaScript
The JavaScript code is stored in "getrss.js" and linked to the HTML document:var xmlHttp; function showRSS(str)
{
xmlHttp=GetXmlHttpObject();
if (xmlHttp==null)
{
alert ("Browser does not support HTTP Request");
return;
}
var url="getrss.php";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlHttp.onreadystatechange=stateChanged;
xmlHttp.open("GET",url,true);
xmlHttp.send(null);
}
function stateChanged()
{
if (xmlHttp.readyState==4 || xmlHttp.readyState=="complete")
{
document.getElementById("rssOutput")
.innerHTML=xmlHttp.responseText;
}
}
function GetXmlHttpObject()
{
var xmlHttp=null;
try
{
// Firefox, Opera 8.0+, Safari
xmlHttp=new XMLHttpRequest();
}
catch (e)
{
// Internet Explorer
try
{
xmlHttp=new ActiveXObject("Msxml2.XMLHTTP");
}
catch (e)
{
xmlHttp=new ActiveXObject("Microsoft.XMLHTTP");
}
}
return xmlHttp;
}
|
The showRSS() Function
Every time an option is selected in the input field this function executes the following:
- Defines the url (filename) to send to the server
- Adds a parameter (q) to the url with the selected option from the drop down box
- Adds a random number to prevent the server from using a cached file
- Calls on the GetXmlHttpObject function to create an XMLHTTP object, and tells the object to execute a function called stateChanged when a change is triggered
- Opens the XMLHTTP object with the given url.
- Sends an HTTP request to the server
The PHP Page
The server page called by the JavaScript code is a PHP file called "getrss.php":<?php //get the q parameter from URL $q=$_GET["q"]; //find out which feed was selected
if($q=="Google")
{
$xml=("http://news.google.com/news?ned=us&topic=h&output=rss");
}
elseif($q=="MSNBC")
{
$xml=("http://rss.msnbc.msn.com/id/3032091/device/rss/rss.xml");
}
$xmlDoc = new DOMDocument(); $xmlDoc->load($xml); //get elements from "<channel>"
$channel=$xmlDoc->getElementsByTagName('channel')->item(0);
$channel_title = $channel->getElementsByTagName('title')
->item(0)->childNodes->item(0)->nodeValue;
$channel_link = $channel->getElementsByTagName('link')
->item(0)->childNodes->item(0)->nodeValue;
$channel_desc = $channel->getElementsByTagName('description')
->item(0)->childNodes->item(0)->nodeValue;
//output elements from "<channel>"
echo("<p><a href='" . $channel_link
. "'>" . $channel_title . "</a>");
echo("<br />");
echo($channel_desc . "</p>");
//get and output "<item>" elements
$x=$xmlDoc->getElementsByTagName('item');
for ($i=0; $i<=2; $i++)
{
$item_title=$x->item($i)->getElementsByTagName('title')
->item(0)->childNodes->item(0)->nodeValue;
$item_link=$x->item($i)->getElementsByTagName('link')
->item(0)->childNodes->item(0)->nodeValue;
$item_desc=$x->item($i)->getElementsByTagName('description')
->item(0)->childNodes->item(0)->nodeValue;
echo ("<p><a href='" . $item_link
. "'>" . $item_title . "</a>");
echo ("<br />");
echo ($item_desc . "</p>");
}
?>
|
Example Explained - The PHP Page
When an option is sent from the JavaScript the following happens:- PHP finds out which RSS feed was selected
- An XML DOM object is created for the selected RSS feed
- The elements from the RSS channel are found and outputted
- The three first elements from the RSS items are looped through and outputted
