Various error messages indicate the existence of a problem with the installation of PMB. It can be, for example, "Call to undefined function" error messages.
PMB needs a number of pre-requisites : for more details on these pre-requisites, go to Chapter 2, Essential information and/or the file YOUR_DIR_PMB/doc/pre_requisite.txt.
This error message indicates that the library PHP_XSLT is not correctly installed.
It is used in : backups, conversion.
Solution : activate the PHP_XSLT library in your PHP configuration. Go to the installation corresponding to your system as well as the chapter Generic installation.