在之前的文章《聊聊PHP中的代理模式（正向代理和反向代理）》中我们介绍了PHP中的代理模式，下面本篇文章带大家了解一下PHP设计模式中的享元模式。
享元模式，“享元”这两个字在中文里其实并没有什么特殊的意思，所以我们要把它拆分来看。“享”就是共享，“元”就是元素，这样一来似乎就很容易理解了，共享某些元素嘛。
GoF定义：运用共享技术有效地支持大量细粒度的对象
GoF类图
代码实现
interface Flyweight
{
public function operation($extrinsicState) : void;
}
class ConcreteFlyweight implements Flyweight
{
private $intrinsicState = 101;
function operation($extrinsicState) : void
{
echo '共享享元对象' . ($extrinsicState + $this->intrinsicState) . PHP_EOL;
}
}
class UnsharedConcreteFlyweight implements Flyweight
{
private $allState = 1000;
public function operation($extrinsicState) : void
{
echo '非共享享元对象：' . ($extrinsicState + $this->allState) . PHP_EOL;
}
}定义共享接口以及它的实现，注意这里有两个实现，ConcreteFlyweigh进行状态的共享，UnsharedConcreteFlyweight不共享或者说他的状态不需要去共享
class FlyweightFactory
{
private $flyweights = [];
public function getFlyweight($key) : Flyweight
{
if (!array_key_exists($key, $this->flyweights)) {
$this->flyweights[$key] = new ConcreteFlyweight();
}
return $this->flyweights[$key];
}
}保存那些需要共享的对象，做为一个工厂来创建需要的共享对象，保证相同的键值下只会有唯一的对象，节省相同对象创建的开销
$factory = new FlyweightFactory(); $extrinsicState = 100; $flA = $factory->getFlyweight('a'); $flA->operation(--$extrinsicState); $flB = $factory->getFlyweight('b'); $flB->operation(--$extrinsicState); $flC = $factory->getFlyweight('c'); $flC->operation(--$extrinsicState); $flD = new UnsharedConcreteFlyweight(); $flD->operation(--$extrinsicState);
客户端的调用，让外部状态$extrinsicState能够在各个对象之间共享
还是说到科技以换壳为本这件事上。毕竟，大家都还是喜欢各种颜色的手机来彰显自己的个性。之前说过，如果每种颜色我们都要做一条生产线的话那岂不是一项巨大的投入。还好，每个型号我们的工厂（享元工厂）只生产最基本的背景壳（对象），然后通过专门的印刷线（状态变化）来进行上色不就好啦！嗯，下一款Iphone早晚也会模仿我们的，看来我们得先把各种金、各种土豪色集齐才行，说不定还能召唤神龙呢！！
完整代码：https://github.com/zhangyue0503/designpatterns-php/blob/master/13.flyweights/source/flyweights.php
果然不出意外的我们还是来发短信，这回的短信依然使用的阿里云和极光短信来进行发送，不过这次我们使用享元模式来实现，这里的享元工厂我们保存了两种不同类型的对象哦，通过内外状态来让它们千变万化吧！
短信发送类图
完整源码：https://github.com/zhangyue0503/designpatterns-php/blob/master/13.flyweights/source/flyweights-message.php
<?php
interface Message
{
public function send(User $user);
}
class AliYunMessage implements Message
{
private $template;
public function __construct($template)
{
$this->template = $template;
}
public function send(User $user)
{
echo '使用阿里云短信向' . $user->GetName() . '发送：';
echo $this->template->GetTemplate(), PHP_EOL;
}
}
class JiGuangMessage implements Message
{
private $template;
public function __construct($template)
{
$this->template = $template;
}
public function send(User $user)
{
echo '使用极光短信向' . $user->GetName() . '发送：';
echo $this->template->GetTemplate(), PHP_EOL;
}
}
class MessageFactory
{
private $messages = [];
public function GetMessage(Template $template, $type = 'ali')
{
$key = md5($template->GetTemplate() . $type);
if (!key_exists($key, $this->messages)) {
if ($type == 'ali') {
$this->messages[$key] = new AliYunMessage($template);
} else {
$this->messages[$key] = new JiGuangMessage($template);
}
}
return $this->messages[$key];
}
public function GetMessageCount()
{
echo count($this->messages);
}
}
class User
{
public $name;
public function GetName()
{
return $this->name;
}
}
class Template
{
public $template;
public function GetTemplate()
{
return $this->template;
}
}
// 内部状态
$t1 = new Template();
$t1->template = '模板1，不错哟！';
$t2 = new Template();
$t2->template = '模板2，还好啦！';
// 外部状态
$u1 = new User();
$u1->name = '张三';
$u2 = new User();
$u2->name = '李四';
$u3 = new User();
$u3->name = '王五';
$u4 = new User();
$u4->name = '赵六';
$u5 = new User();
$u5->name = '田七';
// 享元工厂
$factory = new MessageFactory();
// 阿里云发送
$m1 = $factory->GetMessage($t1);
$m1->send($u1);
$m2 = $factory->GetMessage($t1);
$m2->send($u2);
echo $factory->GetMessageCount(), PHP_EOL; // 1
$m3 = $factory->GetMessage($t2);
$m3->send($u2);
$m4 = $factory->GetMessage($t2);
$m4->send($u3);
echo $factory->GetMessageCount(), PHP_EOL; // 2
$m5 = $factory->GetMessage($t1);
$m5->send($u4);
$m6 = $factory->GetMessage($t2);
$m6->send($u5);
echo $factory->GetMessageCount(), PHP_EOL; // 2
// 加入极光
$m1 = $factory->GetMessage($t1, 'jg');
$m1->send($u1);
$m2 = $factory->GetMessage($t1);
$m2->send($u2);
echo $factory->GetMessageCount(), PHP_EOL; // 3
$m3 = $factory->GetMessage($t2);
$m3->send($u2);
$m4 = $factory->GetMessage($t2, 'jg');
$m4->send($u3);
echo $factory->GetMessageCount(), PHP_EOL; // 4
$m5 = $factory->GetMessage($t1, 'jg');
$m5->send($u4);
$m6 = $factory->GetMessage($t2, 'jg');
$m6->send($u5);
echo $factory->GetMessageCount(), PHP_EOL; // 4说明
原文地址：https://juejin.cn/post/6844903965814259726
作者：硬核项目经理
推荐学习：《PHP视频教程》
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