Why is a class instantiated when the class file is referenced.

[Brianbc]

Working with some OOP, I had an error that I have now traced to inistantiation of a class when the file in which the class is contained is included in any other file. Is this the default/normal behaviour of php, and how do I get myself out of this? I want to create an instance of the class at my own time.
classfile.php

<?php
Class Bibiana{
      Function __Construct(){
      print "I love you \n";
      }

Class Wed{
      Function __Construct(){
      print "And I want to marry you \n";
      print "\t Yours \n";
      print "\t Onang'o \n";
      }
#...
?>

Index.php

#include 'classfile.class.php';

Output of index.php

I love you
And I want to marry you
Onang'o
Yours

[Brianbc]

With a little bit of growing up, I have found the error in one of my scripts. The code in classfile.php is rather long, and I happened to have created an instance of Bibiana at the end of the file.