Dewey Decimal System

<?phpclass dewey {  public $matrix = NULL;  function __construct() {    $this->matrix = array();    for ($i['0'] = '0'; $i['0'] <= '9'; $i['0']++) {      for ($i['1'] = '0'; $i['1'] <= '9'; $i['1']++) {        for ($i['2'] = '0'; $i['2'] <= '9'; $i['2']++) {          $this->matrix[$i['0']][$i['1']][$i['2']] = NULL;        }      }    }  }}$obj['dewey'] = new dewey();print_r($obj['dewey']->matrix);?>