Config.class.php

<?php
class Config
{
  static private $instance = null;
  private $parameters = array();
  
  private function __construct(array $parameters = array())
  {
    $this->parameters = $parameters;    
  }
  
  static public function getInstance(array $parameters = array())
  {
    if (is_null(self::$instance))
    {
      $c = __CLASS__;
      
      self::$instance = new $c($parameters);
    }
    
    return self::$instance;
  }

  public function setParameter($key, $value)
  {
    $this->parameters[$key] = $value;
    
    return $this;
  }  
  
  public function getParameter($key)
  {
    if (!array_key_exists($key, $this->parameters))
    {
      return null;
    }
    
    return $this->parameters[$key];
  }
  
  final public function __clone()
  {
    throw new Exception('Clone instances of this class is forbidden');
  }
  
  final public function __wakeup()
  {
    throw new Exception('Unserializing instances of this class is forbidden');
  }
  
  
}