Class instance method as helper function

[jeff-pruvio]

The PHP Code:

protected function makeSomeText()
{
$php = LightnCandy\LightnCandy::compile($html, array(
'helpers' => array(
"flags": LightnCandy\LightnCandy::FLAG_HANDLEBARS,
"story"=>function($identifier, $options)
{
return $this->getTextForResponse($identifier);
}
)
)
);
}

The Issue:

This doesn't work for me (PHP doesn't like it - referencing $this in a non-object context), and I can't find anything in the documentation about calling a class instance method in a helper.