Treating googlebot as a registered wordpress user?

My anime site is run using wordpress and there are some pages that require users to login before they can access the page- the problem with this is that googlebot will also see the page and index the error message.

How do I treat googlebot as a registered user so it can access the restricted content?

It would be a simple fix; most search engine spider's have various unique user agents. You could simply have your script check to see if the visitor's user agent is a search engine spider agent, and if so skip the error

Bit late here, I'll come online tomorrow afternoon and if you haven't figured it out or if nobody has posted I'll write you up a small section of code. Unfortunately I don't use Wordpress so you will have to adapt it a bit.

But I hope you understand, that it's not secure solution.
For example, there are firefox plugins, which allow to set the same browser agent as googlebot use.
Pretty useful, when you want to access some info without signing up