PHP单例模式 demo

<?php

class single{

static public $db;

private function __construct(){

};

static function getinstance(){

if(!self::$db)

self::$bd = new self();

return self::$db;

}

}

single::getinstance();

//demo 2

class pzhang{

static private $instance;

private $config;

private function __construct($config){

$this->config = $config;

echo "我被实例化了";

}

private function __clone(){

}

static public function getInstance($config){

if(!self::$instance  instanceof self)

self::$instance = new self($config);

return self::$instance;

}

public function getname(){

echo $this->config;

}

}

$adb = pzhang::getInstance(1);

$adb->getname();

//结果   我被实例化了1

?>