PHP arrays store zval ••. The reason for it has to do with references - basically, if you want to do $a =& $b; and then $a = 1 and want for $b be 1 now too, if symbol table for b is storing zval •, there's no way to change it when $a = 1 is executed. However, if b's entry stores pointer to actual zval •, and so does a's entry, when you change that storage to point to zval with 1 instead, both $a and $b would change. Hope I explain it clearly, hard to do it without drawing a picture :)
So, to receive zval ••, you need to pass zval ••• to the hash function. That's why the type in general is void ••, because generic hash (hashes are used for all kinds of things, not only zvals) stores void •, so to receive it you pass void ••.
Just for fun, there are places in the code IIRC where quadruple pointer can be found (see zend_fcall_info_args_save for example). Pretty rare case though, don't remember any place with five-times pointer.
So, to receive zval ••, you need to pass zval ••• to the hash function. That's why the type in general is void ••, because generic hash (hashes are used for all kinds of things, not only zvals) stores void •, so to receive it you pass void ••.
Just for fun, there are places in the code IIRC where quadruple pointer can be found (see zend_fcall_info_args_save for example). Pretty rare case though, don't remember any place with five-times pointer.