Figure out initial balance for bank accounts to avoid them going into negative balance after transfer transactions

balance.php

<?php
function solution($R, $V) {
    // write your code in PHP7.0
    $minA = 0;
    $minB = 0;
    $balA = 0;
    $balB = 0;
    for ($i = 0; $i < strlen($R); $i++) {
            if ($R[$i] == 'A') {
                $balA += $V[$i];
                $balB -= $V[$i];
                if ($balB < $minB) {
                    $minB = $balB;
                }
            } else if ($R[$i] == 'B') {
                $balB += $V[$i];
                $balA -= $V[$i];
                if ($balA < $minA) {
                    $minA = $balA;
                }
            }
        }
        return [-$minA, -$minB ];
}
?>