C# Enemy AI Combat Script Error

Here is a picture of the error - http://i.imgur.com/boEGaTv.png

Here is a picture of the script - http://i.imgur.com/g8YjOv5.png

If you could help that would be great, thanks!

I am assuming that you have a component on the target object called PlayerHealth. What you are wanting to do here is:

PlayerHealth eh = target.GetComponent<PlayerHealth>();