Online PHP editor | refs for oUIJE

<?php function stack(... $items) { foreach ($items as $item) { if ($next = yield $item) { yield from stack(... $next); } else { yield $next; } } } $items = [1,2,3]; $stack = stack(...$items); foreach ($stack as $item) { if ($item == 1) { $stack->send(['negate', -$item]); // push something onto the stack } if ($item == 2) { continue; // remove something from the stack } if ($item == 3) { $stack->send(['exponential', $item ** 2]); // push something onto the stack } if (isset($item)) { var_dump($item); } }