<?php

echo ohmsLaw_1(12, 220, "")."\n";
echo ohmsLaw_1(230, "", 2) ."\n";
echo ohmsLaw_1("", 220, 0.02) ."\n";
echo ohmsLaw_1("", "", 10)."\n";
echo ohmsLaw_1(500, 50, 10)."\n";

function ohmsLaw_1($voltage, $resistance, $current) {
	if ($voltage == "" && $resistance == "" ||
		$voltage == "" && $current == "" ||
		$resistance == "" && $current == "" ||
		$voltage != "" && $resistance != "" && $current != "") {
		return "Invalid";
	}

	if ($voltage == "") {
		$res = $resistance*$current;
	}

	if ($resistance == "") {
		$res = $voltage/$current;
	}
	if ($current == "") {
		$res = $voltage/$resistance;
	}

	return $res;
}

//using empty function
function ohmsLaw_2($voltage, $resistance, $current) {
	if (empty($voltage) && empty($resistance) ||
		empty($voltage) && empty($current) ||
		empty($resistance) && empty($current) ||
		!empty($voltage) && !empty($resistance) && !empty($current)
	) {
		return "Invalid";
	}

	if (empty($voltage)) {
		$res = $resistance*$current;
	}
	if (empty($resistance)) {
		$res = $voltage/$current;
	}
	if (empty($current)) {
		$res = $voltage/$resistance;
	}
	return round($res, 2);
}