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uTools-Manuals/docs/php/list.html
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<title>把数组中的值赋给一组变量</title>
</head>
<body class="docs"><div id="layout">
<div id="layout-content"><div id="function.list" class="refentry">
<div class="refnamediv">
<h1 class="refname">list</h1>
<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">list</span> &mdash; <span class="dc-title">把数组中的值赋给一组变量 </span></p>
</div>
<div class="refsect1 description" id="refsect1-function.list-description">
<h3 class="title">说明</h3>
<div class="methodsynopsis dc-description">
<span class="methodname"><strong>list</strong></span>
( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$var1</code></span>
[, <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$...</code></span>
] ) : <span class="type">array</span></div>
<p class="para rdfs-comment">
像 <span class="function"><a href="array.html" class="function">array()</a></span> 一样，这不是真正的函数，而是语言结构。
<span class="function"><strong>list()</strong></span>
可以在单次操作内就为一组变量赋值。
</p>
<blockquote class="note"><p><strong class="note">Note</strong>:
<p class="para">
在 PHP 7.1.0 之前的版本，<span class="function"><strong>list()</strong></span> 仅能用于数字索引的数组，并假定数字索引从 0 开始。
</p>
</p></blockquote>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
PHP 5 里，<span class="function"><strong>list()</strong></span> 从最右边的参数开始赋值；
PHP 7 里，<span class="function"><strong>list()</strong></span> 从最左边的参数开始赋值。
</p>
<p class="para">
如果你用单纯的变量，不用担心这一点。
但是如果你用了具有索引的数组，通常你期望得到的结果和在
<span class="function"><strong>list()</strong></span> 中写的一样是从左到右的，但在 PHP 5 里实际上不是，
它是以相反顺序赋值的。
</p>
<p class="para">
通常而言，不建议依赖于操作的顺序，在未来可能会再次发生修改。
</p>
</div>
<div class="warning"><strong class="warning">Warning</strong>
<p class="para">
在 <span class="function"><strong>list()</strong></span> 执行过程中修改数组（比如使用 <em>list($a, $b) = $b</em>）将会产生不可预知的结果。
</p>
</div>
</div>
<div class="refsect1 parameters" id="refsect1-function.list-parameters">
<h3 class="title">参数</h3>
<p class="para">
<dl>
<dt>
<code class="parameter">var1</code></dt>
<dd>
<p class="para">
一个变量。
</p>
</dd>
</dl>
</p>
</div>
<div class="refsect1 returnvalues" id="refsect1-function.list-returnvalues">
<h3 class="title">返回值</h3>
<p class="para">
返回指定的数组。
</p>
</div>
<div class="refsect1 changelog" id="refsect1-function.list-changelog">
<h3 class="title">更新日志</h3>
<p class="para">
<table class="doctable informaltable">
<thead>
<tr>
<th>版本</th>
<th>说明</th>
</tr>
</thead>
<tbody class="tbody">
<tr>
<td>7.1.0</td>
<td>
现在可以指定 <span class="function"><strong>list()</strong></span> 中的键。
这就可以解构非数字键或者无顺序的数组。
</td>
</tr>
<tr>
<td>7.0.0</td>
<td>
<a href="migration70.incompatible.html#migration70.incompatible.variable-handling.list.order" class="link">
赋值操作的顺序发生了变化。
</a>
</td>
</tr>
<tr>
<td>7.0.0</td>
<td>
<a href="migration70.incompatible.html#migration70.incompatible.variable-handling.list.empty" class="link">
<span class="function"><strong>list()</strong></span> 表达式不再可以完全为空。
</a>
</td>
</tr>
<tr>
<td>7.0.0</td>
<td>
<a href="migration70.incompatible.html#migration70.incompatible.variable-handling.list.string" class="link">
字符串无法再被拆包（unpack）。
</a>
</td>
</tr>
</tbody>
</table>
</p>
</div>
<div class="refsect1 examples" id="refsect1-function.list-examples">
<h3 class="title">范例</h3>
<p class="para">
<div class="example" id="example-6103">
<p><strong>Example #1 <span class="function"><strong>list()</strong></span> 例子</strong></p>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />$info&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">'coffee'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'brown'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'caffeine'</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">//&nbsp;列出所有变量<br /></span><span style="color: #007700">list(</span><span style="color: #0000BB">$drink</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$color</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #0000BB">$info</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #DD0000">"</span><span style="color: #0000BB">$drink</span><span style="color: #DD0000">&nbsp;is&nbsp;</span><span style="color: #0000BB">$color</span><span style="color: #DD0000">&nbsp;and&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #DD0000">&nbsp;makes&nbsp;it&nbsp;special.\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;列出他们的其中一个<br /></span><span style="color: #007700">list(</span><span style="color: #0000BB">$drink</span><span style="color: #007700">,&nbsp;,&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #0000BB">$info</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #DD0000">"</span><span style="color: #0000BB">$drink</span><span style="color: #DD0000">&nbsp;has&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #DD0000">.\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;或者让我们跳到仅第三个<br /></span><span style="color: #007700">list(&nbsp;,&nbsp;,&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #0000BB">$info</span><span style="color: #007700">;<br />echo&nbsp;</span><span style="color: #DD0000">"I&nbsp;need&nbsp;</span><span style="color: #0000BB">$power</span><span style="color: #DD0000">!\n"</span><span style="color: #007700">;<br /><br /></span><span style="color: #FF8000">//&nbsp;list()&nbsp;不能对字符串起作用<br /></span><span style="color: #007700">list(</span><span style="color: #0000BB">$bar</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #DD0000">"abcde"</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$bar</span><span style="color: #007700">);&nbsp;</span><span style="color: #FF8000">//&nbsp;NULL<br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6104">
<p><strong>Example #2 <span class="function"><strong>list()</strong></span> 用法的一个例子</strong></p>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
&lt;table&gt;<br />&nbsp;&lt;tr&gt;<br />&nbsp;&nbsp;&lt;th&gt;Employee&nbsp;name&lt;/th&gt;<br />&nbsp;&nbsp;&lt;th&gt;Salary&lt;/th&gt;<br />&nbsp;&lt;/tr&gt;<br /><br /><span style="color: #0000BB">&lt;?php<br /><br />$result&nbsp;</span><span style="color: #007700">=&nbsp;</span><span style="color: #0000BB">$pdo</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">query</span><span style="color: #007700">(</span><span style="color: #DD0000">"SELECT&nbsp;id,&nbsp;name,&nbsp;salary&nbsp;FROM&nbsp;employees"</span><span style="color: #007700">);<br />while&nbsp;(list(</span><span style="color: #0000BB">$id</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$name</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$salary</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #0000BB">$result</span><span style="color: #007700">-&gt;</span><span style="color: #0000BB">fetch</span><span style="color: #007700">(</span><span style="color: #0000BB">PDO</span><span style="color: #007700">::</span><span style="color: #0000BB">FETCH_NUM</span><span style="color: #007700">))&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"&nbsp;&lt;tr&gt;\n"&nbsp;</span><span style="color: #007700">.<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">"&nbsp;&nbsp;&lt;td&gt;&lt;a&nbsp;href=\"info.php?id=</span><span style="color: #0000BB">$id</span><span style="color: #DD0000">\"&gt;</span><span style="color: #0000BB">$name</span><span style="color: #DD0000">&lt;/a&gt;&lt;/td&gt;\n"&nbsp;</span><span style="color: #007700">.<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">"&nbsp;&nbsp;&lt;td&gt;</span><span style="color: #0000BB">$salary</span><span style="color: #DD0000">&lt;/td&gt;\n"&nbsp;</span><span style="color: #007700">.<br />&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</span><span style="color: #DD0000">"&nbsp;&lt;/tr&gt;\n"</span><span style="color: #007700">;<br />}<br /><br /><br /></span><span style="color: #0000BB">?&gt;<br /></span><br />&lt;/table&gt;</span>
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6105">
<p><strong>Example #3 使用嵌套的 <span class="function"><strong>list()</strong></span></strong></p>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br /></span><span style="color: #007700">list(</span><span style="color: #0000BB">$a</span><span style="color: #007700">,&nbsp;list(</span><span style="color: #0000BB">$b</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$c</span><span style="color: #007700">))&nbsp;=&nbsp;array(</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;array(</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">));<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$b</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$c</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
</div>
<div class="example-contents screen">
<div class="cdata"><pre>
int(1)
int(2)
int(3)
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6106">
<p><strong>Example #4 在 <span class="function"><strong>list()</strong></span> 中使用数组索引</strong></p>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br /><br />$info&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #DD0000">'coffee'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'brown'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'caffeine'</span><span style="color: #007700">);<br /><br />list(</span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">0</span><span style="color: #007700">],&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">],&nbsp;</span><span style="color: #0000BB">$a</span><span style="color: #007700">[</span><span style="color: #0000BB">2</span><span style="color: #007700">])&nbsp;=&nbsp;</span><span style="color: #0000BB">$info</span><span style="color: #007700">;<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$a</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">?&gt;</span>
</span>
</pre></div>
</div>
<div class="example-contents"><p>
产生如下输出（注意单元顺序和 <span class="function"><strong>list()</strong></span> 语法中所写的顺序的比较）：
</p></div>
<div class="example-contents"><p>Output of the above example in PHP 7:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(3) {
[0]=&gt;
string(6) &quot;coffee&quot;
[1]=&gt;
string(5) &quot;brown&quot;
[2]=&gt;
string(8) &quot;caffeine&quot;
}
</pre></div>
</div>
<div class="example-contents"><p>Output of the above example in PHP 5:</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(3) {
[2]=&gt;
string(8) &quot;caffeine&quot;
[1]=&gt;
string(5) &quot;brown&quot;
[0]=&gt;
string(6) &quot;coffee&quot;
}
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6107">
<p><strong>Example #5 <span class="function"><strong>list()</strong></span> 和索引顺序定义</strong></p>
<div class="example-contents"><p>
<span class="function"><strong>list()</strong></span> 使用 array 索引的顺序和它何时定义无关。
</p></div>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$foo&nbsp;</span><span style="color: #007700">=&nbsp;array(</span><span style="color: #0000BB">2&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'a'</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">'foo'&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'b'</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">0&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'c'</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">$foo</span><span style="color: #007700">[</span><span style="color: #0000BB">1</span><span style="color: #007700">]&nbsp;=&nbsp;</span><span style="color: #DD0000">'d'</span><span style="color: #007700">;<br />list(</span><span style="color: #0000BB">$x</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$y</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$z</span><span style="color: #007700">)&nbsp;=&nbsp;</span><span style="color: #0000BB">$foo</span><span style="color: #007700">;<br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$foo</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$x</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$y</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">$z</span><span style="color: #007700">);</span>
</span>
</pre></div>
</div>
<div class="example-contents"><p>
得到以下输出（注意比较 <span class="function"><strong>list()</strong></span> 所写的元素顺序）：
</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
array(4) {
[2]=&gt;
string(1) &quot;a&quot;
[&quot;foo&quot;]=&gt;
string(1) &quot;b&quot;
[0]=&gt;
string(1) &quot;c&quot;
[1]=&gt;
string(1) &quot;d&quot;
}
string(1) &quot;c&quot;
string(1) &quot;d&quot;
string(1) &quot;a&quot;
</pre></div>
</div>
</div>
</p>
<p class="para">
<div class="example" id="example-6108">
<p><strong>Example #6 带键的 <span class="function"><strong>list()</strong></span></strong></p>
<div class="example-contents"><p>
从 PHP 7.1.0 开始，<span class="function"><strong>list()</strong></span> 可以包含显式的键，可赋值到任意表达式。
可以混合使用数字和字符串键。但是不能混合有键和无键不能混用。
</p></div>
<div class="example-contents">
<div class="phpcode"><pre><span style="color: #000000">
<span style="color: #0000BB">&lt;?php<br />$data&nbsp;</span><span style="color: #007700">=&nbsp;[<br />&nbsp;&nbsp;&nbsp;&nbsp;[</span><span style="color: #DD0000">"id"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"name"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'Tom'</span><span style="color: #007700">],<br />&nbsp;&nbsp;&nbsp;&nbsp;[</span><span style="color: #DD0000">"id"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"name"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #DD0000">'Fred'</span><span style="color: #007700">],<br />];<br />foreach&nbsp;(</span><span style="color: #0000BB">$data&nbsp;</span><span style="color: #007700">as&nbsp;[</span><span style="color: #DD0000">"id"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$id</span><span style="color: #007700">,&nbsp;</span><span style="color: #DD0000">"name"&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$name</span><span style="color: #007700">])&nbsp;{<br />&nbsp;&nbsp;&nbsp;&nbsp;echo&nbsp;</span><span style="color: #DD0000">"id:&nbsp;</span><span style="color: #0000BB">$id</span><span style="color: #DD0000">,&nbsp;name:&nbsp;</span><span style="color: #0000BB">$name</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;<br />}<br />echo&nbsp;</span><span style="color: #0000BB">PHP_EOL</span><span style="color: #007700">;<br />list(</span><span style="color: #0000BB">1&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$second</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3&nbsp;</span><span style="color: #007700">=&gt;&nbsp;</span><span style="color: #0000BB">$fourth</span><span style="color: #007700">)&nbsp;=&nbsp;[</span><span style="color: #0000BB">1</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">2</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">3</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">4</span><span style="color: #007700">];<br />echo&nbsp;</span><span style="color: #DD0000">"</span><span style="color: #0000BB">$second</span><span style="color: #DD0000">,&nbsp;</span><span style="color: #0000BB">$fourth</span><span style="color: #DD0000">\n"</span><span style="color: #007700">;</span>
</span>
</pre></div>
</div>
<div class="example-contents"><p>以上例程会输出：</p></div>
<div class="example-contents screen">
<div class="cdata"><pre>
id: 1, name: Tom
id: 2, name: Fred
2, 4
</pre></div>
</div>
</div>
</p>
</div>
<div class="refsect1 seealso" id="refsect1-function.list-seealso">
<h3 class="title">参见</h3>
<p class="para">
<ul class="simplelist">
<li class="member"><span class="function"><a href="each.html" class="function" rel="rdfs-seeAlso">each()</a> - 返回数组中当前的键／值对并将数组指针向前移动一步</span></li>
<li class="member"><span class="function"><a href="array.html" class="function" rel="rdfs-seeAlso">array()</a> - 新建一个数组</span></li>
<li class="member"><span class="function"><a href="extract.html" class="function" rel="rdfs-seeAlso">extract()</a> - 从数组中将变量导入到当前的符号表</span></li>
</ul>
</p>
</div>
</div></div></div></body></html>
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