Improved named arguments

I don't understand why there should be an exception here.

`array_slice()` definition reads as follow: `array array_slice ( array $array , int $offset [, int $length = NULL [, bool $preserve_keys = false ]] )`

So, if it were a Twig function, it would be perfectly legitimate to call it like this: `array_slice(array(), offset=null, preserve_keys=true)`, which is your example here. There is no need to explicitly define the value of `length` as there is a default value, so it's optional.

Or am I missing something?