Do you still need the `use` keyword to actually make a proper closure?

i.e.
```php
function adder($x){
  return function addto($y) use ($x) {
    return $y + $x;
  }
}
```

Also, is this:

```php
function outer_function ($arg_1 = null) { // $arg_1 is optional
  function inner_function($arg_2 = 'two') { // $arg_2 will default to 'two'
  }
}
```
missing a "return" somewhere?