Extending SWFButton

Hi all-


I have a feeling something like this came up before, apologies if so, but I 
can't find anything in the archives so...

The question is: why can't I successfully add a function to a class which 
inherits from SWFButton (or indeed SWFMovie, SWFSprite etc)?

For example, this works nicely:

<?php

class ParentClass {
        function ParentClass()
        {
                echo "creating ParentClass<br />";
        }
}

class ChildClass extends ParentClass {
        function newfunc()
        {
                echo "in newfunc<br />";
        }
}

$cc = new ChildClass();
$cc->newfunc();

?>

produces the expected output:

> creating ParentClass
> in newfunc

and yet, if ChildClass extends SWFButton, I discover:

> Fatal error: Call to undefined function: newfunc() in /path/to/script.php etc

Maybe it's my understanding of OO principles which is lacking, but I never came 
across this before. Any ideas?

I've made that example as short as possible, but I also get exactly the same 
whether or not I create a constructor for ChildClass and call 
$this->SWFButton() within it. So if I would have:

<?php

class ChildClass extends SWFButton{

        function ChildClass()
        {
                $this->SWFButton(); // or $this = new SWFButton();
                //optional other stuff
        }
        function newfunc()
        {
                echo "in newfunc<br />";
        }
}

$cc = new ChildClass();
$cc->newfunc();

?>

This throws exactly the same fatal error. Again, I switch it back to extend 
from ParentClass and all works fine.


Cheers for any help guys,
Simon