Remove islands (Google interview)

!index.php

<?php

require 'Map.php';

$map = new Map([
    [1, 1, 0, 0, 0, 0, 0, 1],
    [0, 1, 0, 0, 1, 1, 1, 0],
    [1, 0, 1, 0, 0, 0, 0, 0],
    [1, 0, 0, 1, 1, 0, 1, 1],
    [0, 0, 1, 1, 1, 0, 0, 1],
]);

$map->goOverTopBorder(fn($i, $j) => $map->removeIslandAt($i, $j));
$map->goOverBottomBorder(fn($i, $j) => $map->removeIslandAt($i, $j));
$map->goOverLeftBorder(fn($i, $j) => $map->removeIslandAt($i, $j));
$map->goOverRightBorder(fn($i, $j) => $map->removeIslandAt($i, $j));

$map->output();

Map.php

<?php

class Map
{
    private $map;
    
    function __construct($map)
    {
        $this->map = $map;
    }
    
    public function get($i, $j)
    {
        return isset($this->map[$i][$j]) ? $this->map[$i][$j] : null;
    }
    
    public function set($i, $j, $value)
    {
        $this->map[$i][$j] = $value;
    }
    
    public function rowCount()
    {
        return count($this->map);
    }
    
    public function colCount()
    {
        return count($this->map[0]);
    }
    
    private function goOverPath($index, $direction, $callback)
    {
        $start = 0;
        $end = $direction === 'horizontal' ? $this->colCount() : $this->rowCount();

        for ($i = $start; $i < $end; $i++) {
            if ($direction === 'horizontal') {
                $callback($index, $i);
            }
            else if ($direction === 'vertical') {
                $callback($i, $index);
            }
            else {
                break;
            }
        }
    }
    
    public function goOverTopBorder($callback)
    {
        $this->goOverPath(0, 'horizontal', $callback);
    }
    
    public function goOverBottomBorder($callback)
    {
        $bottomRowIndex = $this->rowCount() - 1;

        $this->goOverPath($bottomRowIndex, 'horizontal', $callback);
    }
    
    public function goOverLeftBorder($callback)
    {
        $this->goOverPath(0, 'vertical', $callback);
    }
    
    public function goOverRightBorder($callback)
    {
        $rightColumnIndex = $this->colCount() - 1;

        $this->goOverPath($rightColumnIndex, 'vertical', $callback);
    }
    
    public function removeIslandAt($i, $j)
    {
        if ($this->get($i, $j) === 1) {
            $this->set($i, $j, 0);

            $this->removeIslandAt($i, $j - 1);
            $this->removeIslandAt($i, $j + 1);
            $this->removeIslandAt($i - 1, $j);
            $this->removeIslandAt($i + 1, $j);
        }
    }
    
    public function output()
    {
        foreach ($this->map as $row) {
            echo implode(' ', $row) . "\n";
        }
    }
}