Regular expression image generation

gistfile1.php

<?php

/**
 * Example: php file.php 6 "1"
 */

class Rec {

  protected $grid = [];
  protected $fourDirectionMap = [[0, 0], [1, 0], [1, 1], [0, 1]];
  protected $size;
  protected $regex;

  public function __construct($aSize = 3, $aRegex = '') {
    $this->size = pow(2, $aSize);
    $this->regex = $aRegex;

    $this->emptyGrid();
    $this->gen($this->size, 0, 0);
    $this->printGrid();
  }

  protected function emptyGrid() {
    for ($y = 0; $y < $this->size; $y++) {
      for ($x = 0; $x < $this->size; $x++) {
        $this->grid[$x][$y] = 0;
      }
    }
  }

  protected function printGrid() {
    echo "\n\n";
    for ($y = 0; $y < $this->size; $y++) {
      for ($x = 0; $x < $this->size; $x++) {
        $isMatch = preg_match('/' . $this->regex . '/', $this->grid[$x][$y]);
        echo $isMatch ? '  ' : 'O ';
//        echo $this->grid[$x][$y] . ' ';
      }
      echo "\n";
    }
    echo "\n\n";
  }

  protected function gen($size, $startX, $startY, $segment = '') {
    $newSize = $size >> 1;

    if ($newSize > 1) {
      $this->gen($newSize, $startX, $startY, $segment . '1');
      $this->gen($newSize, $startX + $newSize, $startY, $segment . '2');
      $this->gen($newSize, $startX + $newSize, $startY + $newSize, $segment . '3');
      $this->gen($newSize, $startX, $startY + $newSize, $segment . '4');
    }
    else {
      foreach ($this->fourDirectionMap as $index => $direction) {
        $this->grid[$startX + $direction[0]][$startY + $direction[1]] = $segment . ($index + 1);
      }
    }
  }
}

new Rec($argv[1], $argv[2]);