PHP8.0新特性之Named Parameters（命名参数）

命名参数，PHP8.0允许在函数/方法调用中使用命名参数。

简单地说，就是可以在调用函数或方法传递参数时，可以给参数取一个与函数参数或方法一样的名字。

位置参数

先来看看PHP8.0之前，使用位置参数的案例

<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">say</span>(<span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$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">echo</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><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">say</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'王五'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">12</span>); <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 王五12</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">say</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">12</span>, <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'李四'</span>); <span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 12李四</span></span>

使用位置参数，得到的是完全不一样的结果，有了命名参数后，调用函数或方法时，位置就可以随意放置了。

命名参数案例

自定义函数

<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">say</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">$name</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$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">echo</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</span>;</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px">}</span><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">// 结果都是 李四19</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">say</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'李四'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">age</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">19</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">say</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">age</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">19</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'李四'</span>);</span>

需要注意的是，调用时传递参数的名字需要和方法定义时的名字一致。

内置函数

<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">// 默认位置</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">$res1</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">str_contains</span>(<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'php是世界上最好语言'</span>, <span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'php'</span>);</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(98, 151, 85) !important">// 使用命名参数后，位置可以发生变化</span></span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"><span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$res2</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">str_contains</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">haystack</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'php是世界上最好语言'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">needle</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(224, 108, 117) !important">$res3</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">str_contains</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">needle</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'php'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">haystack</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'php是世界上最好语言'</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">// 输出结果都是 true</span></span>

PHP8.0以后的新函数支持命名参数；小于8的版本，绝大多数函数不支持命名参数，也就是说，命名参数不向前兼容。

参数跳过

<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">say</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">$name</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">int</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</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">18</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$sex</span> <span style="box-sizing: border-box;color: rgb(86, 182, 194) !important">=</span> <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">1</span>) {</span><br></br><span style="box-sizing: border-box;color: rgb(171, 178, 191);padding-right: 0.1px"> <span style="box-sizing: border-box;color: rgb(198, 120, 221) !important">echo</span> <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$name</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$age</span>, <span style="box-sizing: border-box;color: rgb(224, 108, 117) !important">$sex</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">// 全部都传递参数</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">say</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'李四'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">age</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">19</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">sex</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;color: rgb(98, 151, 85) !important">// 修改性别，使用命令参数跳过age参数</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">say</span>(<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">name</span>:<span style="box-sizing: border-box;color: rgb(152, 195, 121) !important">'王美丽'</span>, <span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">sex</span>:<span style="box-sizing: border-box;color: rgb(209, 154, 102) !important">2</span>);</span>

使用命名参数时，可以为指定的参数赋值。

需要注意的是，可选参数一定要在必选参数的后面；必选无法跳过，必须传递参数。

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