单例/单态模式(Singleton Pattern)

百度词条的解释

http://baike.baidu.com/view/1859857.htm

<?php
//单例模式
final class PSV {
	private $loan = false;
	private static $myPSV;
	public function getInstance() {
		if(!isset(self::$myPSV)) {
			self::$myPSV = new PSV();
		}
		return self::$myPSV;
	}
	public function setLoan() {
		$this->loan = !$this->loan;
	}
	public function getLoan() {
		return $this->loan;
	}
	//禁止外部new或者clone对象
	private function __construct() {}
	private function __clone() {}
}
$myPSV = PSV::getInstance();
var_dump($myPSV->getLoan());
$myPSV->setLoan();
var_dump($myPSV->getLoan());
?>

//单态模式
class PSV {
	private static $loan = false;
	public function setLoan() {
		self::$loan = !self::$loan;
	}
	public function getLoan() {
		return self::$loan;
	}
}
$myPSV = new PSV();
var_dump($myPSV->getLoan());
$myFriendPSV = new PSV();
$myFriendPSV->setLoan();
var_dump($myPSV->getLoan());