Online PHP editor | output for AoKJO

<?php $sum = function ($a, $b) { return $a + $b; }; function calc($value_or_function, array $buffer = []) { if (is_callable($value_or_function)) { if (count($buffer) === 0) { throw new \InvalidArgumentException('Not enough parameters.'); } return array_reduce(array_slice($buffer, 1), $value_or_function, $buffer[0]); } return static function ($otherValue) use ($buffer, $value_or_function) { return calc($otherValue, array_merge($buffer, [$value_or_function])); }; } echo calc(5)(4)(3)($sum), PHP_EOL; echo calc(5)(2)(2)('pow');