Check the php.ini. You may need make a few changes there to fit your environment.
I hope you get it working because these functions are very cool and useful to the network admin.
Have you played with the php snmp functions?
If not, I have some of my notes available online that may help you http://pccs-linux.com/phplinux/php_part4.html
The notes are based on ucd-snmp- applications, and php on nix.
I've also hacked a couple of php/snmp web apps..
email me offline if you're interested in looking at the code for these apps
Again check you php.ini
CT