Performing Client-Side XSL Transformations
By Tony Marston2005-12-12
Software changes
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Making the change was actually quite straightforward. One difference is that when I create my XML document instead of this:
<?xml version="1.0" encoding="UTF-8"?>
<root>
<foobar>
....
</foobar>
</root>
I must add an extra line to identify that an XSL transformation is required, and the URL of the XSL stylesheet that should be used to perform the transformation, as shown below:
<?xml version="1.0" encoding="UTF-8"?>
<?xml-stylesheet type="text/xsl" href="HTTP://www.tonymarston.net/foobar.xsl"?>
<root>
<foobar>
....
</foobar>
</root>
This extra line is not required for server-side XSL transformations as the XML and XSL documents are supplied as separate inputs to the XSLT processor.
The second change was to tell my software which type of XSL processing is required - client-side or server-side. I decided to make this feature switchable at runtime so that it could be turned on or off at will. To do this I look for an argument in the $_GET array with the name csxslt (for Client-Side XSL Transformations) which can have a value of either ON or OFF.
The following codes takes any value from the $_GET array (if present) and stores it in the $_SESSION array where it is preserved until the end of the session.
if (!array_key_exists('XSLT_client_side', $_SESSION)) {
$_SESSION['XSLT_client_side'] = FALSE;
} // if
if (isset($_GET['csxslt'])) {
$_SESSION['XSLT_client_side'] = $_GET['csxslt'];
} // if
When the XML document is complete I decide what to do with it using the following code:
if (is_true($_SESSION['XSLT_client_side'])) {
// send XML file to the client for transformation there
XSLclient($xml_string);
} else {
// transform XML document into HTML using XSL file
XSLTransform($xml_string, $xsl_file);
} // if
It is the XSLclient() function that sends the raw XML to the client's browser:
function XSLclient ($xml_string)
// send the XML file to the client so that it can be transformed into HTML there
{
// set charset to display accented characters correctly
header('content-type: application/xml; charset=UTF-8');
// disable any caching by the browser
header('Expires: Mon, 14 Oct 2002 05:00:00 GMT'); // Date in the past
header('Last-Modified: ' .gmdate("D, d M Y H:i:s") .' GMT'); // always modified
header('Cache-Control: no-store, no-cache, must-revalidate'); // HTTP 1.1
header('Cache-Control: post-check=0, pre-check=0', false);
header('Pragma: no-cache'); // HTTP 1.0
echo $xml_string;
return;
} // XSLclient
While the pages were transformed without problem by IE6 there were a few difficulties with Firefox which were resolved as follows:
- Due to the fact that I am outputting XHTML 1.0 Strict, all the XSL stylesheets, including those which which are merged in at runtime with
<xsl:include>, must contain a specification for the default namespace, as in the following:<xsl:stylesheet version="1.0"<
xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
xmlns="http://www.w3.org/1999/xhtml"> - XHTML is case-sensitive (stupid idea!) so all references to CSS selectors must be in the same case in which they were defined. As some of my definitions were in upper case and all my references are in lower case I had to make a few small adjustments to my CSS files in order to eliminate the last problems.
There. That's all there is to it.
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