These statements...
$b=$Array1[$a]; $c=$Array2[$b]; $d=$Array3[$c];
combined into one statement like:
$d=$Array3[$Array2[$Array1[$a]]]
???
I know my example isn't valid, but is it possible to do this kind of consolidation?
As in nesting? Yes, and in fact your example is valid but for a missing terminating semi-colon.
Doh! You are right...
You know it's getting late when you post a question to a forum before even trying it in your code first... :o