PHP Example - AJAX and XML

AJAX can be used for interactive communication with an XML file.

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:

Select a CD: Select a CD: Bob Dylan Bonnie Tyler Dolly Parton CD info will be listed here...

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)

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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:

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("" . $cd->item($i)->nodeName . ": "); echo($cd->item($i)->childNodes->item(0)->nodeValue); echo(" "); } } ?>

When the CD query is sent from the JavaScript to the PHP page, the following happens:

1. PHP creates an XML DOM object
2. Find all elements that matches the name sent from the JavaScript
3. Output the album information (send to the "txtHint" placeholder)