AJAX can be used for interactive communication with an XML file.
AJAX XML Example #
The following example will demonstrate how a web page can fetch information from an XML file with AJAX:
Example Explained – The HTML Page #
When a user selects a CD in the dropdown list above, a function called “showCD()” is executed. The function is triggered by the “onchange” event:
<html>
<head>
<script>
function showCD(str) {
if (str=="") {
document.getElementById("txtHint").innerHTML="";
return;
}
var xmlhttp=new XMLHttpRequest();
xmlhttp.onreadystatechange=function() {
if (this.readyState==4 && this.status==200) {
document.getElementById("txtHint").innerHTML=this.responseText;
}
}
xmlhttp.open("GET","getcd.php?q="+str,true);
xmlhttp.send();
}
</script>
</head>
<body>
<form>
Select a CD:
<select name="cds" onchange="showCD(this.value)">
<option value="">Select a CD:</option>
<option value="Bob Dylan">Bob Dylan</option>
<option value="Bee Gees">Bee Gees</option>
<option value="Cat Stevens">Cat Stevens</option>
</select>
</form>
<div id="txtHint"><b>CD info will be listed here...</b></div>
</body>
</html>
The showCD() function does the following:
- Check if a CD 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 “getcd.php”.
The PHP script loads an XML document, “cd_catalog.xml“, runs a query against the XML file, and returns the result as HTML:
<?php
$q=$_GET["q"];
$xmlDoc = new DOMDocument();
$xmlDoc->load("cd_catalog.xml");
$x=$xmlDoc->getElementsByTagName('ARTIST');
for ($i=0; $i<=$x->length-1; $i++) {
//Process only element nodes
if ($x->item($i)->nodeType==1) {
if ($x->item($i)->childNodes->item(0)->nodeValue == $q) {
$y=($x->item($i)->parentNode);
}
}
}
$cd=($y->childNodes);
for ($i=0;$i<$cd->length;$i++) {
//Process only element nodes
if ($cd->item($i)->nodeType==1) {
echo("<b>" . $cd->item($i)->nodeName . ":</b> ");
echo($cd->item($i)->childNodes->item(0)->nodeValue);
echo("<br>");
}
}
?> When the CD query is sent from the JavaScript to the PHP page, the following happens:
- PHP creates an XML DOM object
- Find all <artist> elements that matches the name sent from the JavaScript
- Output the album information (send to the “txtHint” placeholder)
