abstract：<?php namespace app\index\controller; //单例模式:一个类只允许被实例化一次 class Database { private function __construct() {
<?php
namespace app\index\controller;
//单例模式:一个类只允许被实例化一次
class Database
{
private function __construct()
{
}
private function __clone()
{
// TODO: Implement __clone() method.
}
protected static $instance = null;
public static function getInstance(){
if(is_null(static::$instance)){
static::$instance = new static();
}
return static::$instance;
}
}
$connect3 = Database::getInstance();
$connect4 = Database::getInstance();
echo ($connect3 instanceof Database)?'是':'不是';
echo '<hr>';
echo ($connect4 instanceof Database)?'是':'不是';
echo '<hr>';
echo ($connect3 === $connect4)?'=':'不=';
Correcting teacher：查无此人Correction time：2019-05-09 13:59:28
Teacher's summary：完成的不错。编程有很多编程模式，多了解，能更好的学习。继续加油。