<?php

// Example usage:
function mytheme_preprocess_node(&$vars) {
  $wrapper = new CantTouchThis($vars['node']);
  $wrapper->protect('type', true);
  $vars['node'] = $wrapper;
}



class CantTouchThis {

  private $protected = array();
  private $object;

  public function __construct($object) {
    $this->object = $object;
  }

  public function protect($property_name, $alert = false) {
    $this->protected[$property_name] = $alert;
  }

  public function __set($key, $value) {
    if(!isset($this->protected[$key])) {
      $this->object->$key = $value;
    }
    elseif($this->protected[$key]) {
      list(, $caller) = debug_backtrace(0, 2) + array(null, null);
      if($caller) {
        $msg = strtr('Attempt to change property {property} to value "{value}", initiated in function {func} (file {file}, line {line})', array(
          '{property}' => (string) $key,
          '{value}'    => (string) $value,
          '{func}'     => $caller['function'],
          '{file}'     => $caller['file'],
          '{line}'     => $caller['line'],
        ));
        throw new Exception($msg);
      }
    }
  }

  public function __get($key) {
    return $this->object->$key;
  }

}