If your PHP version is >=4.1.x use phpinfo() to see if php was compiled with --enable-xslt --with-xslt-sablot, then of course get the extension and reference it in php.ini. If it was not configured with --enable-xslt --with-xslt-sablot, you will need to either recompile PHP or get a package with the features included. Of course this is platform specific I would reckon where tsinka asked you for your OS, etc.