Fix Helloworld app

```
$app = $hasApc && apc_fetch('app-helloworld');
```

`$app` would be boolean every time because `false && any` is absolutely `false` and `true && object` is evaluated as `true`. This logic can success the 1st time call (still not in APC) but 2nd or later failure.

```
$ php -v
PHP 5.4.11 (cli) (built: Feb  7 2013 12:22:21) 
Copyright (c) 1997-2013 The PHP Group
Zend Engine v2.4.0, Copyright (c) 1998-2013 Zend Technologies
    with Xdebug v2.2.1, Copyright (c) 2002-2012, by Derick Rethans
$ php -a
php > var_dump(true && new stdClass);
bool(true)
```