If you receive an error “Class ‘XsltProcessor’ not found” in your website then it means that XSL extension is not installed on your server. You will require installing PHP XSL extension.
Error: Fatal error: Class ‘XsltProcessor’ not found in /path/to/filename.php on line XXX
Depending on the server platform / operating system, the installation method may differ.
If you are using cPanel control panel, you will require to recompile your Apache and PHP to enable this PHP extension.