PHP8.1新特性之Enumerations(枚举)

作者: 温新

分类: 【PHP基础】

阅读: 4153

时间: 2022-02-20 14:06:36

我是温馨,一名PHPer

文档:https://www.php.net/manual/zh/language.enumerations.php

枚举,或称 “Enum”,能够让开发者自定义类型为一系列可能的离散值中的一个。 在定义领域模型中很有用,它能够“隔离无效状态”(making invalid states unrepresentable)。

在 PHP 中, 枚举是一种特殊类型的对象。Enum 本身是一个类(Class), 它的各种条目(case)是这个类的单例对象,意味着也是个有效对象 —— 包括类型的检测,能用对象的地方,也可以用它。

枚举基础

enum是一个限定类,需以enum关键字开头,后面跟可选的string|int

枚举定义

一个枚举可以定义零个或多个case,且没有最大数量限制。

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 不初始化直接定义</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 初始化赋值</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 错误案例,若初始化值,</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 则必须指定枚举类型的变量类型</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span>

enum的基础操作

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 定义枚举</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 使用枚举</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 获取枚举元素的值</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">value</span>; <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 1</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 获取枚举元素的key</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>;  <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// Start</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 也可以对家对象来操作</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$obj</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span>;</span>

枚举类型不能被实例化,也没有构造函数。若使用new去实例化,则会报致命错误。

回退枚举,通过值来获取枚举实例

回退枚举仅能回退到 intstring 里的一种类型, 且同时仅支持使用一种类型(就是说,不能联合 int|string)。 回退条目必须是唯一的;两个回退条目不能有相同的标量。

回退枚举实现了内置的BackedEnum interface,暴露两个额外的方法:

1)from(int|string): self 能够根据标量返回对应的枚举条目。 如果找不到该值,会抛出ValueError。主要用于输入标量为可信的情况,使用一个不存在的枚举值,可以考虑为需终止应用的错误。

2)tryFrom(int|string): ?self 能够根据标量返回对应的枚举条目。 如果找不到该值,会返回 null。 主要用于输入标量不可信的情况,调用者需要自己实现默认值的逻辑或错误的处理。

通过 from 来获取枚举类

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 使用from通过值来获取枚举类</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">print_r</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">from</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>));</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 使用不存在的值获取枚举类</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">print_r</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">from</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">404</span>));</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// Fatal error: Uncaught ValueError: 404 is not a valid backing value for enum "Status" </span></span>

通过 tryFrom 来获取枚举类

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">var_dump</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">tryFrom</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">404</span>)); <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// NULL</span></span>

定义枚举方法

枚举(包括纯粹枚举、回退枚举)还能包含方法, 也能实现 interface。 如果 Enum 实现了 interface,则其中的条目也能接受 interface 的类型检测。

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    </span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 枚举中定义方法</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">test</span>()</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// match php8新特性</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">return</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">match</span> (<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span>) {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">      <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">self</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'开始状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">      <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">self</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>  <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'结束状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     };</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    }</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 调用枚举方法</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">test</span>(); <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 开始状态</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">test</span>();   <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 结束状态</span></span>

枚举中实现接口

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    </span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">interface</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">TestInterface</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">cry</span>();</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">interface</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">DemoInterface</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">say</span>();</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>: <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">implements</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">TestInterface</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">DemoInterface</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">cry</span>()</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">      <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">return</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">self</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    }</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">say</span>()</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">      <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">return</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">match</span> (<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span>) {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">         <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">self</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'开始状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">         <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">self</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>  <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'结束状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     };</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   }</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">cry</span>();</span>

枚举使用trait

枚举也能使用 trait,行为和 class 一样。 留意在枚举中 use trait 不允许包含属性。 只能包含方法、静态方法。 包含属性的 trait 会导致 fatal 错误。

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    </span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">trait</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">Test</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">test</span>(<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$_this</span>)</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">       <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">return</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">match</span> (<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$_this</span>) {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">          <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$_this</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'开始状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">          <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$_this</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>  <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=></span> <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'结束状态'</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     };</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    }</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>: <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   use</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Test</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   public</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">getStatus</span>()</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 调用trait中定义的方法</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">     <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">return</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">test</span>(<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   } </span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">getStatus</span>();</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">getStatus</span>();</span>

判断一个枚举是否存在

enum_exists判断一个枚举是否存在

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>: <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">   case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">var_dump</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum_exists</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'Status'</span>));</span>

枚举序列化

枚举的序列化不同于对象。 尤其是它们有新的序列化代码: "E",指示了 enum 条目名称。

<span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important"><?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">php</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">    </span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">enum</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>: <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Start</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    case</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>   <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">serialize</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Status</span>::<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">End</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// E:10:"Status:End";</span></span>

枚举和对象的差异

尽管 enum 基于类和对象,但它们不完全支持对象相关的所有功能。 尤其是枚举条目不能有状态。

枚举的特性

1)禁止构造、析构函数。

2)不支持继承。无法 extend 一个 enum。

3)不支持静态属性和对象属性。

4)由于枚举条目是单例对象,所以不支持对象复制

5)不能使用魔术方法

与对象相同的功能

1)Public、private、protected 方法、静态方法、常量。

2)enum 可以 implement 任意数量的 interface。

3)枚举和它的条目都可以附加注解。

4)常量 __CLASS____FUNCTION__ 的功能和平时无差别

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