How to use variable in closure functions in php?

I am using intervention for php for image manipulations. Is it possible to apply font size and color to text through a variable like this? I have calculated $fontsize and $color above this but it says undefined variable

$img->text($string, $item['x'], $top, function($font) {
                        $font->file('assets/fonts/Roboto-Medium.ttf');
                        $font->size($fontsize);
                        $font->color($color);
                        $font->align('left');
                        $font->valign('top');
                    });

via Chebli Mohamed