[RESOLVED] Callback Functions

[tomcatexodus]

I'm having an issue with callback functions, specifically storing them...

If I have a class:

class myObject{

    protected $callback;

    public function __construct($callbackFunction){
        $this->callback = $callbackFunction;
        .
        .
        .
    }

    public function doSomething($args){
        if(is_callable($this->callback)){
            return $this->callback($args);
        }
    }

} 

And I try doing this:

function foo($arg){
    return strtoupper($arg);
}

$myNewObject = new myObject("foo");
echo $myNewObject->doSomething("bar"); //should echo BAR 

I end up with an error:

Fatal Error: Call to undefined method MyObject::callback() in ...

The is_callable() is succeeding, but the actual callback function call is the line failing with that error.

This isn't exactly what I'm doing obviously, but its a replicate of the code. Any ideas?