Test question for Gumroad

gistfile1.php

<?php
// 1, 4, 6, 3, 2

function findPivot($arr, $checkIndex = NULL){
	//if only one value is passed into array, that is the pivot point because nothing on the left == nothing on the right
	if(count($arr) == 1) return 0;

	$lastCheckIndex = count($arr) - 1;
	if(
		$checkIndex > $lastCheckIndex ||
		( 
			$checkIndex == $lastCheckIndex && 
			array_sum(array_slice($arr, 0, $checkIndex)) != array_sum(array_slice($arr, $checkIndex + 1)) 
		)
	){
		return -1;
	}

	if(!$checkIndex){
		return findPivot($arr, 1);
	} elseif(array_sum(array_slice($arr, 0, $checkIndex)) != array_sum(array_slice($arr, $checkIndex + 1))){
		return findPivot($arr, $checkIndex + 1);
	} else {
		return $checkIndex;
	}
}

var_dump(findPivot(array(1, 4, 6, 3, 2)));
die('done.' . PHP_EOL);