HTMLify

class Solution {

    /**
     * @param Integer[] $nums
     * @return Integer
     */
    function pivotIndex($nums) {
        $left_sum = 0;
        $total_sum = array_sum($nums);
        for($i=0; $i<count($nums); $i++){
            if($left_sum == $total_sum - $left_sum - $nums[$i])
                return $i;
            $left_sum += $nums[$i];
        }
        return -1;
    }
}