If you see in your installation error:
Fatal error: Call to undefined function mysql_connect
It means, that in your php is not installed mysql extension, which is mandatory for Post Affiliate Pro.
Often user see, that php files are working in web browser, but e.g. from cron or when executing script manually from commandline, it doesn't work.
This is caused by fact, that webser could use another php or another php.ini is used.
Resolution is to add support of mysql extension also to commandline version of php.