AJAX can be used to communicate interactively with XML files.
The following example will demonstrate how a web page reads information from an XML file through AJAX:
When the user selects a CD in the drop-down list above, a function named "showCD()" is executed. This function is triggered by the "onchange" event:
<html><head><script>function showCD(str){ if (str=="") { document.getElementById("txtHint").innerHTML=""; return; } if (window.XMLHttpRequest) { // IE7+, Firefox, Chrome, Opera, Safari browsers execute xmlhttp=new XMLHttpRequest(); } else { // IE6, IE5 The browser executes xmlhttp=new ActiveXObject("Microsoft.XMLHTTP"); } xmlhttp.onreadystatechange=function() { if (xmlhttp.readyState==4 && xmlhttp.status==200) { document.getElementById("txtHint"). innerHTML=xmlhttp.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=" Bonnie Tyler">Bonnie Tyler</option><option value="Dolly Parton">Dolly Parton</option></select></form><div id="txtHint"><b>CD info will be listed here...</ b></div></body></html>The showCD() function performs the following steps:
Check if a CD is selected
Create XMLHttpRequest object
Create a function that executes when the server response is ready
Send a request to a file on the server
Note the parameter (q) added to the end of the URL (containing the contents of the drop-down list)
The server page called above through JavaScript is a PHP file named "getcd.php".
The PHP script loads the XML document, "cd_catalog.xml", runs the query against the XML file, and returns the results in HTML:
<?php$q=$_GET["q"];$xmlDoc = new DOMDocument();$xmlDoc->load("cd_catalog.xml");$x=$xmlDoc->getElementsByTagName('ARTIST');for ($i=0; $i<=$x->length-1; $i++){ // Process element node if ($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;$i++){ // Process element node if ($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 JavaScript to the PHP page, what happens:
PHP creates XML DOM object
Find names in all <artist> elements that match the data passed by JavaScript
Output the album information and send back the "txtHint" placeholder