Sure it won't create an instance of Array, but if you're using an Array to also be an associative array then really I think JSON is the least of your worries.
tl;dr: Google search is starting to suck.
That NAT won't let you do this is a weakness of the technology, not a strength. Protecting a user from themselves is an interface issue, and one that should be possible for an experienced user circumvent if needed. Otherwise you may as well say that Bash shouldn't allow globbing - after all, a user might accidentally type rm * in the wrong directory.
A downside to NAT for a small home network? How about when you have two or more servers both listening on port 22, and externally you have to remember which port you plucked from thin air in order to be able to get to it? This of course being multiplied by the number of servers and number of services being run on them. It's not the end of the world (for a small network) but it offers no benefit except for conserving IPs.
*(Yes, yes, yes, I'm well aware I've just described one-to-one NAT, but I think it's pretty clear that that's not the type of NAT I'm arguing against.)
NAT solves ONE problem: more devices than public IPs. Any perceived security benefits are purely incidental and can be solved (better) by a firewall.
But I reiterate: PHP probably isn't the language for you. I understand your position, as I'm completely anal about code being free from all warnings too. However; I'm also of the opinion that strict type checking actually provides comparatively little benefit. When I fix bugs in our codebase it's almost never due to type mismatches, in fact I can only think of two instances ever where I've thought strong typing would have prevented a bug. On the one hand you may claim that's two bugs too many, but on the other hand that's several years of IMO faster development gained by not having to jump through hoops.
I've yet to use a language with a full type inference system, but it seems like that may be a pretty awesome compromise.
Arithmetic is being able to count up to twenty without taking off your shoes. -- Mickey Mouse