miniMVC/sys/core/traits/Singleton.php

<?php
/**
 * MiniMVC
 *
 * Convention-based micro-framework for PHP
 *
 * @package		miniMVC
 * @author 		Timothy J. Warren
 * @copyright	Copyright (c) 2011 - 2012
 * @link 		https://github.com/aviat4ion/miniMVC
 * @license 	http://philsturgeon.co.uk/code/dbad-license 
 */

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

namespace miniMVC;

/**
 * Singleton pattern
 *
 * @package miniMVC
 * @subpackage System
 */
trait Singleton {

	use Generic;

	/**
	 * Singleton object
	 *
	 * @var self
	 */
	protected static $instance;
	
	/**
	 * Protected constructor for creating the one instance
	 */
	abstract protected function __construct();
	 
	/**
	 * PHP magic method that is called when an object is treated as a function
	 *
	 * @param array $params
	 * @return self
	 */
	public static function __invoke($params = [])
	{
		return self::get_instance($params);
	}
	
	// --------------------------------------------------------------------------
	
	/**
	 * Singleton getter function
	 *
	 * @return self
	 */
	public static function &get_instance()
	{
		if ( ! isset(self::$instance)) 
		{
			$class = __CLASS__;
		
			self::$instance = new $class;
		}
		
		return self::$instance;
	}
	
	// --------------------------------------------------------------------------
	
	/**
	 * Magic function called when cloning an object
	 */
	public function __clone()
	{
		trigger_error('Clone is not allowed.', E_USER_ERROR);
	}
}

// End of Singleton.php