Global variables in closure scope

[tomcatexodus]

Is there a way to ensure that top-level variables are visible in the scope of a closure, without needing to declare them global in the closure itself?

For example; if I'm working with code using a syntax such as this:

    $a = 0; //A TOP-LEVEL VARIABLE

    Alpha::create('myAlpha')
        ->bind(DataSingleton::getInstance()
            ->query('c')
        )
        ->addBeta('myBeta', function($obj){
            $obj->bind(DataSingleton::getInstance()
                    ->query('d')
                )
                ->addGamma('myGamma', function($obj){
                    $obj->bind(DataSingleton::getInstance()
                            ->query('a')
                        )
                        ->addDelta('myDelta', function($obj){
                            $obj->bind(DataSingleton::getInstance()
                                ->query('b')
                            );
                        });
                })
                ->addGamma('myGamma', function($obj){

                    $a++; //OUT OF MY SCOPE

                    $obj->bind(DataSingleton::getInstance()
                            ->query('c')
                        )
                        .
                        .
                        . 

Now of course normally one would need to declare it as global or use the $GLOBALS superglobal. The closures are being called from within a method as such:

        public function __construct($name, $closure = null){
            $this->_name = $name;
            is_callable($closure) ? $closure($this) : null;
        } 

Providing a jQuery-ish syntax. This is all very simplified for use as an example.

TL;DR: How can I implicitly declare as global the closure scoped variables.