If you try to simplify it to an equation, you end up with 
$is_valid = ($a ? ($d ? $b && $c : !$b && !$c || !$b && $c || $b && !$
+c) : !($b && $c && $d);

[download]
which is totally unreadable and unmaintainable, doubly so when you use the full variable names. So don't do this :)

In reply to Re: Testing for 16 possible combinations with 4 pull-down menus by ikegami
in thread Testing for 16 possible combinations with 4 pull-down menus by softcotton

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