PHP
Example - AJAX RSS Reader
An RSS
Reader is used to read RSS Feeds.
AJAX
RSS Reader
The
following example will demonstrate an RSS reader, where the RSS-feed is loaded
into a webpage without reloading:
RSS-feed
will be listed here...
Example Explained
- The HTML Page
When a user
selects an RSS-feed in the dropdown list above, a function called
"showRSS()" is executed. The function is triggered by the
"onchange" event:
<html>
<head>
<script>
function
showRSS(str) {
if (str.length==0) {
document.getElementById("rssOutput").innerHTML="";
return;
}
if (window.XMLHttpRequest) {
// code for IE7+, Firefox, Chrome, Opera,
Safari
xmlhttp=new XMLHttpRequest();
} else {
// code for IE6, IE5
xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
}
xmlhttp.onreadystatechange=function() {
if (this.readyState==4 &&
this.status==200) {
document.getElementById("rssOutput").innerHTML=this.responseText;
}
}
xmlhttp.open("GET","getrss.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>
<form>
<select
onchange="showRSS(this.value)">
<option
value="">Select an RSS-feed:</option>
<option
value="Google">Google News</option>
<option
value="NBC">NBC News</option>
</select>
</form>
<br>
<div
id="rssOutput">RSS-feed will be listed here...</div>
</body>
</html>
The
showRSS() function does the following:
Check if an
RSS-feed is selected
Create an
XMLHttpRequest object
Create the
function to be executed when the server response is ready
Send the
request off to a file on the server
Notice that
a parameter (q) is added to the URL (with the content of the dropdown list)
The PHP File
The page on
the server called by the JavaScript above 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=="NBC") {
$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>");
}
?>
When a
request for an RSS feed is sent from the JavaScript, the following happens:
Check which
feed was selected
Create a new
XML DOM object
Load the RSS
document in the xml variable
Extract and
output elements from the channel element
Extract and
output elements from the item elements
