Variable In Controller Then Function

For some reason my variable doesn't pass to my SMS function?

public function visitor_signin(Request $request)
{

$data = $request->first_name;
$mobile = $request->mobile;

SMS::send('text::invite', ['data' => $data], function($sms) {
 $sms->to($mobile);
});

}

I get the error: Undefined variable: mobile

via Chebli Mohamed