[PHP] Classes, instances and NULL

[Oliver Hitz]

Hi all,

I have stumbled across something odd related to classes, instances and
NULL in PHP 4. Apparently, an instance of a class that doesn't contain
any variables is always equal to NULL.

  class MyClass {
    function anyFunction() {
      ...
    }
  }

  $c = new MyClass();
  if ($c == null) {
    print "is \$c really null?";
  }

`is_null($c)' however, returns `false', as one would expect.

As soon as the class contains a variable, the `$c == null' comparison
returns false.

Is there any logical reason why the comparison with the `==' operator
returns `true'? I don't know about the internals of PHP, but I think
this might be related to implementation details (e.g. instances of
classes being associative arrays). However, from an OOP point of view
this behaviour seems rather weird.

I may not be the first to notice this. I couldn't find anything in the
mailing list, if there has already been a discussion about this, just
point me to the right direction.

Thanks
Oliver

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