The issue you report means that the php module for payflow pro on the php installation is missing, you must recompile php with payflow pro option.
Please check
http://www.php.net/manual/en/ref.pfpro.php
These functions were added in PHP 4.0.2.
I had this same error but let my ISP know and the recompiled php with Payflow Pro and it is working flawlessly with the very latest SnapShot of OSC 2.2
Joe