PHP_UML relies on the PHP extension XSL for certain output formats. Please modify your php.ini to enable this extension.
You can ignore this warning. If you really don't want to see it, add a "date.timezone" configuration line in your php.ini
Some modeling tools expect XMI in version 1. By default, PHP_UML generates XMI in version 2. So use the switch -x to specify the version 1, as described in Command line interface