private $_data = array();

public function __get($name) {
  if (array_key_exists($name, $this->_data)) {
    return $this->_data[$name];
  } else {
    return false;
  }
}

public function __set($name, $value) {
  $this->_data[$name] = $value;
}

[...]


//----------------------------------------------------------------------

$obj = new MyClass();
$obj->__set("min", 1);
$obj->__set("max", 8);

$obj->__get("min");
$obj->__get("max");