simple_map.php

<?php

class Map
{
    const TREE = 0x1;
    const GRESS = 0x2;
    const BRIDGE = 0x4;
    const BLOCKED = 0x8;

    protected $size_x;
    protected $size_y;
    protected $char_length;

    public function __construct($size_x = 2048, $size_y = 2048, $bit_length = 16)
    {
        $this->size_x = $size_x;
        $this->size_y = $size_y;
        $this->char_length = (int) ($bit_length / 8);
        $this->map = str_repeat("\0", $size_x * $size_y * $this->char_length);
    }

    public function getOffset($x, $y)
    {
        return $x * $this->size_y + $y * $this->char_length;
    }

    public function getCell($x, $y)
    {
        $str = substr($this->map, $this->getOffset($x, $y), $this->char_length);
        $cell = 0;
        for ($i = 0; $i < $this->char_length; $i++) {
            $cell |= (ord($str[$i]) << ($i * 8));
        }
        return $cell;
    }

    public function setCell($x, $y, $cell)
    {
        $offset = $this->getOffset($x, $y);
        for ($i = 0; $i < $this->char_length; $i++) {
            $this->map[$offset + $i] = chr(($cell >> ($i * 8)) & 0xFF);
        }
    }

    public function setCellProperty($x, $y, $flag)
    {
        $cell = $this->getCell($x, $y);
        $cell |= $flag;
        $this->setCell($x, $y, $cell);
    }
}

$map = new Map;
$map->setCellProperty(5, 10, Map::BLOCKED);
$map->setCellProperty(5, 10, Map::GRESS);
var_dump((bool) ($map->getCell(5, 10) & Map::BLOCKED));
var_dump((bool) ($map->getCell(5, 10) & Map::GRESS));
var_dump((bool) ($map->getCell(5, 10) & Map::BRIDGE));
var_dump($map->getCell(5, 9));
var_dump($map->getCell(5, 11));