<?php

var_dump(isOrthogonal([1, 2], [2, -1]))."\n";
var_dump(isOrthogonal([3, -1], [7, 5]))."\n";
var_dump(isOrthogonal([1, 2, 0], [2, -1, 10]))."\n";

function isOrthogonal($arr1, $arr2) {
	$prod = 0;
	$count = count($arr1);
	for ($i = 0; $i < $count; $i++) {
		$prod += $arr1[$i]*$arr2[$i];
	}
	return $prod == 0? true:false;
}

/*
//JS solution:
function isOrthogonal(ar1, arr2){
	let prod=0;
	let count=arr1.length;
	for (i=0; i<count; i++){
		prod+=arr1[i]*arr2[i];
	}
	return prod==0? true; false;
}
*/