单例模式:只有一个实例,不能在new出多个,不能克隆出多个
<?php
class Mysql{
//该属性用来保存实例
private static $conn;
//构造函数为private,防止创建对象
private function __construct(){
self::$conn = mysqli_connect('localhost','root','root');
}
//创建一个用来实例化对象的方法
public static function getInstance(){
if(!(self::$conn instanceof self)){
self::$conn = new self;
}
return self::$conn;
}
public static function shu(){
echo self::$ceshi;
}
//防止对象被复制
public function __clone(){
trigger_error('Clone is not allowed !');
}
}
$mysql = Mysql::getInstance();
?>