PHP5 and XSLTProcessor: disable validation

Hi, i'm currently learning php by implementing a blog system. This uses xsl for transformation to (x)html. It is working so far, but it is slow. As far as i can see the XSLTProcessor is doing a validation. Doing the same transformation with xsltproc (the command line tool for libxslt) takes about the same time. Adding the parameter --novalid to xsltproc speeds up things dramatically. Is there any possibility/option/parameter/whatever to stop XSLTProcessor validation? I've found nothing in the documentation. I hope i'm not wrong here. I'm new to php as well as to this list :) regards Siegfried Gipp