Well, as mentioned, not in this specific case we have.

```
$ php -a
Interactive shell

php > $var = array(false, null, 0, '', array());
php > foreach (array_keys($var) as $key) { var_dump(isset($var[$key])); }
bool(true)
bool(false)
bool(true)
bool(true)
bool(true)
php >
```

I don't see how it can be faster. It checks whether the hashmap key exists and proceeds on verifying the value.