PHP设计模式

1.单例模式

<?php
class Mysql{
    private static $instance = null;
    private $conn;
    //构造方法，设置为private，不允许通过new获得对象
    private function __construct(){
        $conn = mysql_connect("localhost", "root", "");
    }
    public static function getInstance(){
        if(!self::$instance instanceof self){
            self::$instance = new self;
        }
        return self::$instance;
    }
    //阻止用户复制对象实例
    private function __clone(){}
}
$db = Mysql::getInstance();
?>

2.工厂模式

<?php
//定义个抽象类，让子类去继承实现它
abstract class Operation{
    abstract public function getValue($num1, $num2);//子类必须实现此方法
}

//加法类
class OperationAdd extends Operation{
    public function getValue($num1, $num2){
        return $num1+$num2;
    }
}
//减法类
class OperationSub extends Operation{
    public function getValue($num1, $num2){
        return $num1-$num2;
    }
}
//乘法类
class OperationMul extends Operation{
    public function getValue($num1, $num2){
        return $num1*$num2;
    }
}
//除法类
class OperationDiv extends Operation{
    public function getValue($num1, $num2){
        try{
            if($num2 == 0){
                throw new Exception("除数不能为0");
            }else{
                return $num1/$num2;
            }
        }catch(Exception $e){
            echo "错误信息:".$e->getMessage();
        }
    }
}
/**
 *  工厂类，主要用来创建对象
 *  功能：根据输入的运算符号，工厂就能实例出合适的对象
 */
class Factory{
    public static function createObj($operate){
        switch($operate){
            case '+':
                return new OperationAdd();
                break;
            case '-':
                return new OperationSub();
                break;
            case '*':
                return new OperationMul();
                break;
            case '/':
                return new OperationDiv();
                break;
        }
    }
}
$test=Factory::createObj('/');
$result=$test->getValue(23,0);
echo $result;
?>

 3.观察者模式

<?php
/**
 * 观察者模式
 */
class Paper{
    private $_observers = array();

    public function register($sub){
        $this->_observers[] = $sub;
    }

    public function trigger(){
        if(!empty($this->_observers)){
            foreach($this->_observers as $observer){
                $observer->update();
            }
        }
    }
}

interface Observerable(){
    public function update();
}

class Subscriber implements Observerable{
    public function update(){
        echo "OK";
    }
}

$paper = new Paper();
$paper->register(new Subscriber());
$paper->trigger();
?>

 4.命名链模式