Please note i cant support any bugs. I am not a php programmer it was really hard for me to this much. Feel free to discuss fix / modify code
-Change nothing just upload files to webserver punbb root
-then make folder named sitemap and chmode 777
at shell or ssh ,write
php sitemap.php
php sitemap1.php
your new xml files will be at sitemap folder
This is for punbb 1.2.x