gistfile1.php

<?php

function elkc()
{
	static $elkc;

	if ($elkc === null)
		$elkc = new Elk_Container;

	return $elkc;
}

/**
 * @todo replace with Pimple
 */
class Elk_Container extends ArrayObject
{
	protected $_lazy_load = array();
	protected $_protected = array();

	public function __construct()
	{
		parent::__construct(array(), ArrayObject::ARRAY_AS_PROPS);
	}

	public function offsetGet($index)
	{
		if (isset($this->_lazy_load[$index]))
		{
			$this->offsetSet($index, $this->_lazy_load[$index]());
			unset($this->_lazy_load[$index]);
		}

		return parent::offsetGet($index);
	}

	public function offsetExists($index)
	{
		return parent::offsetExists($index) || isset($this->_lazy_load[$index]);
	}

	public function offsetUnset($index)
	{
		if (!$this->isProtected($index))
		{
			parent::offsetUnset($index);
			unset($this->_lazy_load[$index]);
		}
	}

	public function offsetSet($index, $newval)
	{
		if (!$this->isProtected($index))
			parent::offsetSet($index, $newval);
	}

	/**
	 * Add a class to be lazily loaded
	 * @param string $key
	 * @param string $class
	 * @return Elk_Container
	 */
	public function lazyLoad($key, $class, $file = null)
	{
		$function = '';

		if (!empty($file))
		{
			$function .= 'require_once \'' . $file . '\';';
		}

		$function .= 'return new ' . $class . ';';

		$this->_lazy_load[$key] = create_function('', $function);

		return $this;
	}

	/**
	 * Check if a property is protected (you can't change it)
	 * @param string $property
	 * @return bool
	 */
	public function isProtected($property)
	{
		return isset($this->_protected[$property]);
	}

	public function protect($property)
	{
		$this->_protected[$property] = true;
		return $this;
	}
}

$elkc = elkc();

$elkc['a'] = true;
$elkc->lazyLoad('b', 'stdClass');
$elkc->lazyLoad('c', 'ArrayObject');
$elkc->c['hello'] = 'World';
$elkc->protect('c');

var_dump($elkc['a'], $elkc['b'], $elkc->c, $elkc);