OOP Class Interaction

I have been writing OOP programs for the past couple years. Over these years I have run into the same problem, I have solved the problem in many different ways. I was wondering if there is a recommended way to solve the problem I have listed below. To keep it simple, lets say I have 3 classes. A main class, an error class and a log class. The classes are laid out as:

              MAIN
                  |
      ----------------
      |                    |
ERROR          LOG

Now I want error to write a message to the log file. Solution 1

      Store the Main class in a Session variable. And the access the Log through main.

     $_SESSION["Main"]->Log->Write_Error("My Error");

Solution 2

     Almost the same as above.  I store main in a Session Variable but the I create a global function to access log.

      function Write_Error($Message)
      {
             $_SESSION["Main"]->Log->Write_Error($Message);
     }

This ways saves coding time because I don't have to write out the long session reference. I know there are more ways to do this. But every way I can think of requires you to store the main class in a session variable to access log. Is there a way to access a parent class or a parents parent without doing what I did above ? Thanks in advance, Jonathan Pitcher