Despite Netbeans 6.9 doesn’t exist in the repositories you can upgrade to the new version.
Just download the new version and install it. You can do that by simply :chmod +x netbeans-6.9-ml-php-linux.sh ./netbeans-6.9-ml-php-linux.sh
After installing and at the first run it will detect older versions and import configuration and projects… And voilà!
If you want you can now uninstall the older version. Done!