I'm trying to implement the hitcounter function for images and placed
in my album.php file. When it tries to execute it gets fatal error because it can't find the hitcounter function. I've looked at the obvious php function files but cant find it.

Well, if you can't find the function and you get an error because PHP can't find the function then it probaby does not exist. Perhaps you are looking for getHitcounter()?

There are numerous posts in this forum that instruct me to add the code
in order to add the hitcounter functionality. I know I need to use getHitCounter() to display the hits. I've read the documentation on this site and can't find a function called hitcounter in any of the php function files. Has it been renamed? How do I actually turn it on so it will record when someone views an image? Maybe Im misunderstanding the other posts.

Hitcounters are recorded automatically. All you have to do (if you wish) is to display the counters.

Just a suggestion--looking at how the distributed themes do things is a useful exercise.

I thought the hitcounters for images were stored in the zp_images table and when I query that table
directly all rows have hitcounter=0. Are they in a different table?