Question3Toptal

Question3Toptal.php

<?php
function solution($A)
{
    $sum = 0;

    while (count($A)) {

        // remove the last part
        array_pop($A);

        // remove and sum the first line
        $sum += array_sum((array)array_shift($A));

        // remove and sum the last column
        array_walk($A, function(&$line) use (&$sum) {
            $sum += array_pop($line);
        });

        // remove the first column
        array_walk($A, function(&$line) use (&$sum) {
            array_shift($line);
        });

        $sum += array_sum((array)array_pop($A));

        // remove first line
        array_shift($A);

        // remove the last column
        array_walk($A, function(&$line) use (&$sum) {
            array_pop($line);
        });

        // remove and sum the first column
        array_walk($A, function(&$line) use (&$sum) {
            $sum += array_shift($line);
        });

    }

    return $sum;
}
?>