Count Negative Integers in Row/Column-Wise Sorted Matrix

countNegatives.php

function countNegatives($matrix) {
    if (!is_array($matrix)) {
        throw new TypeError('The matrix is not an array');
    }

    //rows
    $rows = count($matrix);

    // columns
    $columns = (array_sum(array_map('count', $matrix)) / $rows);

    $count = 0;
    $i = 0;
    $j = $columns - 1;
    
    $sortedMatrix = [];
    foreach ($matrix as $row) {
        sort($row, SORT_NUMERIC);
        $sortedMatrix[] = $row;
    }

    while (($j >= 0) && ($i < $rows)) {

        if ($sortedMatrix[$i][$j] < 0) {
            $count += $j +1;
            $i++;
        } else {
            $j--;
        }
    }
    return $count;
}