PHP8.0新特性之Union Types(联合类型)

什么是Union Types

简单地说，就是一值在内存中可能有存在多种类型的表示。

Union Types演示

?string

在PHP8中，可以使用?|type来忽略一个为null的值。PHP7中string|null variables的写法已经被放弃，PHP8中使用?|type来表示。

<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">// PHP8写法</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">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">show</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">string</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>):<span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">?</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">string</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">{</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(232, 191, 106) !important">    var_dump</span>(<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</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">$name</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">show</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'自如初'</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">show</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">null</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// PHP7写法，未进行测试</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">function</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">show</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">string</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">|</span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">null</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>):<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">string</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">null</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(232, 191, 106) !important">    var_dump</span>(<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">    return</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$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;color: rgb(209, 154, 102) !important">show</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'自如初'</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">show</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">null</span>);</span>

类属性

一个属性既可以string类型，也可以是array类型

<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">class</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">Person</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">__construct</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(209, 154, 102) !important">string</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>,</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">  <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">public</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</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(209, 154, 102) !important">string</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">|</span><span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">array</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$hobbies</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"> )</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"> {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$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">name</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">age</span>  <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">   <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$this</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">hobbies</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$hobbies</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"> }</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box"></span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$p1</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">new</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Person</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'自如初'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">18</span>, <span style="box-sizing: border-box;color: rgb(152, 195, 121) !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(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$p1</span><span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">-></span><span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$p2</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">new</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">Person</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'PHP博客'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">18</span>, [<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'vue'</span>,<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'js'</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(224, 108, 117) !important">$p2</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">hobbies</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>

我是温新

每天进步一点，就一点点