use function and use const, not just use for classes

Namespaced code can import classes with use, but until 5.6 functions and constants had no equivalent. Calling a namespaced function meant either fully qualifying it every time or relying on the fallback to global scope, which is a lookup PHP performs on every call.

namespace AppReport;

use function AppSupportformat_money;
use const AppSupportCURRENCY;

echo format_money($total, CURRENCY);

Importing the function also removes the global fallback: PHP no longer has to check the current namespace first and then the global one. The performance difference is small, but the readability difference is not — the import block now lists every external thing the file touches, functions included.