<?php

interface Shape{
    public function draw();
}

class Circle implements Shape{
    private $color;
    private $num;

    public function __construct($color){
        $this->color = $color;
    }

    public function draw(){
        echo "this is a {$this->color} circle {$this->num} n";
    }

    public function setNum($num){
        $this->num = $num;
    }
}

class ShapeFactory{
    public static $shape_arr = [];

    public static function getShape($color){
        if(!array_key_exists($color,static::$shape_arr)){
            static::$shape_arr[$color] = new Circle($color);
        }
        return static::$shape_arr[$color];
    }
}

$colors = ["Red", "Green", "Blue", "White", "Black"];

for ($i=0; $i < 20; $i++) {
    $a = $i%5;
    $circle = ShapeFactory::getShape($colors[$a]);
    $circle->setNum($i);
    $circle->draw();
}

输出

this is a Red circle 0
this is a Green circle 1
this is a Blue circle 2
this is a White circle 3
this is a Black circle 4
this is a Red circle 5
this is a Green circle 6
this is a Blue circle 7
this is a White circle 8
this is a Black circle 9
this is a Red circle 10
this is a Green circle 11
this is a Blue circle 12
this is a White circle 13
this is a Black circle 14
this is a Red circle 15
this is a Green circle 16
this is a Blue circle 17
this is a White circle 18
this is a Black circle 19

  注意：享元模式适用于对象存在时间不长的情况，就像例子中画一个圆形只要这个圆形画完后其对象就没有意义啦，这时我们将这个对象的属性改变后成为一个新的对象是可以的。假设我们是在一个创建游戏人物的场景中使用，当创建了某个类型的英雄人物对象之后，我们想要再创建一个相同类型不同属性的英雄人物时，则不适合使用这种设计模式，因为后来的英雄人物对象会是前一个对象改变属性后生成的，这将导致之前的英雄就不存在啦。