$registry = Registry::getInstance();
$registry->set('key', 'value');
echo $registry->get('key'); //prints value

<?php
  /**
   * PHP5 Registry Class
   *
   * @package Registry
   * @author Travis Crowder <travis.crowder@spechal.com>
   * @see MIT License
   * @copyright Travis Crowder
   */

  /**
   *  Registry
   *
   *  The Registry class is used to store values in a global fashion
   *  @final
   *  @see ArrayObject
   */
  final class Registry extends ArrayObject {

    /**
     * Instance object
     *
     * @staticvar object Registry
     */
    static private $_instance = NULL;

    /**
     *  @access private
     *  @var mixed Array to hold the values.
     */
    private $_registry;

    /**
     * Using Singleton pattern with public constructor due to parent class
     *
     * @access public
     * @return void
     */
    public function __construct($array = array(), $flags = parent::ARRAY_AS_PROPS){
      parent::__construct($array, $flags);
    }

    /**
     * Singleton accessor to the object
     *
     * @access public
     * @return Registry $instance Instance of the object
     */
    static public function getInstance(){
      if(self::$_instance === NULL){
        self::$_instance = new Registry;
      }
      return self::$_instance;
    }

    /**
     *  Get method
     *
     *  @access public
     *  @return mixed Element in the registry
     */
    static public function get($key){
      $instance = self::getInstance();
      if(!$instance->checkOffset($key))
        return false; #throw new Exception($key . ' is not set in the registry');
      return $instance->returnOffset($key);
    }

    /**
     *  Set method
     *
     *  Accessor method used to set a value to a registry key.
     *  @access public
     *  @static
     *  @return void
     */
    static public function set($key, $value){
      $instance = self::getInstance();
      $instance->setOffset($key, $value);
    }

    /**
     *  Method to set ArrayObject offset
     *
     *  This method sets the ArrayObjects value
     *  @access protected
     *  @return void
     */
    protected function setOffset($key, $value){
      $this->_registry[$key] = $value;
    }

    /**
     *  Check ArrayObject offset
     *
     *  Method to check if an ArrayObject Registry index has a value.
     *  @param string $key Index of Registry to access
     *  @access protected
     *  @return bool
     */
    protected function checkOffset($key){
      if(isset($this->_registry[$key]))
        return true;

      return false;
    }

    /**
     *  Return method
     *
     *  Method to return the value of a Registry index
     *  @access protected
     *  @return mixed Value of Registry index.
     */
    protected function returnOffset($key){
      return $this->_registry[$key];
    }

    /**
     *  Dump method
     *
     *  Method to dump the contents of the Registry to the screen via print_r
     *  @access public
     *  @return void
     */
    public function dump(){
      print_r($this->_registry);
    }

  }