XSL and XSLT Page 41

XSL is the XML-based language for describing stylesheets. You've probably used Cascading Style Sheets (CSS) when working with static HTML. CSS is used to handle the presentation of an HTML document, and HTML is used for layout of the page. Within the XML world, XSL provides the instructions to an XSLT processor, describing how to handle XML data. So XSL performs a similar function as CSS.

An XSL document is well-formed XML and conforms with the XSL namespace. Although we've already looked at what makes an XML document well-formed, we haven't looked at namespaces. An XML namespace is a set of predefined elements. By creating a standardized list of elements, all XSLT processors will know, for example, that <xsl:comment></xsl:comment& ;amp;gt; will create a comment in the target document, like <!-- --> in HTML. All you need to know is to include namespace declaration, xmlns:xsl="http://www.w3.org/1999/XSL/Transform ", in the <xsl:stylesheet> element. You can find more information about namespaces online at: http://www.w3.org/TR/REC-xml-names/.

The different parts of XSL are described using the same naming conventions as XML, so within XSL the building blocks are called elements and attributes.

In this section of the chapter we will be using a tiny part of the XSL recommendation. XSL is a large subject and there are whole books written about it. We will be using enough XSL to render an XML document as an HTML table. For more information on XSL, see XSLT Programmer's Reference 2nd Edition from Wrox (ISBN 1-861005-06-7).

Sablotron

To use XSL with PHP you will need to use Sablotron. Sablotron, also known as Sablot, is a PHP extension that provides support for XSL, XSLT, and XPath, and is maintained by the Ginger Alliance (http://www.gingerall.com/). Sablotron requires the Expat parser to be already installed. If you've gotten this far through the chapter and have played with the SAX examples, then you've got Expat installed.

Installation and Verifying XSL

If Sablotron appeared in the phpinfo.php earlier, then it is already installed. If not, you can download the libraries from the Ginger Alliance (http://www.gingerall.com/).

UNIX Installation

After downloading the rpms take a look at the README file that is listed with the rpms. The installation instructions are in the README file. Install the rpm by typing:

rpm -i sablotron-0.6x-x.i386.rpm

or

rpm -i sablotron-devel-0.6x-x.i386.rpm

After installing Sablotron, you can re-compile PHP with the XSLT extension, add a –with-sablot string to your configuration string, re-compile, and install PHP. If you are having problems refer to the annotated manual on the PHP.net site: http://www.php.net/manual/en/ref.xslt.php.

Windows Installation

The download of PHP 4.0.6 should contain all the appropriate dlls to install Sablotron. They are in the PHP\dlls\ directory of the distribution.

To install Sablotron with PHP and Apache:

• Stop Apache if it is running.

• Extract the following dlls into the C:\Windows\System\ folder if you are running Windows98 or C:\WINNT\System32\ if you are running WindowsNT/2000:
  • expat.dll

  • sablot.dll

  • xmlparser.dll

  • xmltok.dll

• Open your php.ini file and remove the comment from the line ;extension=php_sablot.dll. Save the php.ini file.

• Restart Apache.

• Run the code.

The Windows installer for IIS automatically places these files in their appropriate places.

XSL Example Code

For this example we need to have three files in the same directory:

• travel.xml

• travel.xsl

• xslt_travel.php

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