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91 lines
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HTML
91 lines
4.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
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<html>
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<head>
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<meta http-equiv="content-type" content="text/html; charset=UTF-8">
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<title>Gets the first key of an array</title>
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</head>
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<body class="docs"><div id="layout">
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<div id="layout-content"><div id="function.array-key-first" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">array_key_first</h1>
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<p class="verinfo">(PHP 7 >= 7.3.0)</p><p class="refpurpose"><span class="refname">array_key_first</span> — <span class="dc-title">Gets the first key of an array</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.array-key-first-description">
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<h3 class="title">说明</h3>
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<div class="methodsynopsis dc-description">
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<span class="methodname"><strong>array_key_first</strong></span>
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( <span class="methodparam"><span class="type">array</span> <code class="parameter">$array</code></span>
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) : <span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span></div>
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<p class="para rdfs-comment">
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Get the first key of the given <code class="parameter">array</code> without affecting
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the internal array pointer.
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.array-key-first-parameters">
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<h3 class="title">参数</h3>
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<dl>
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<dt>
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<code class="parameter">array</code></dt>
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<dd>
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<p class="para">
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An array.
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</p>
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</dd>
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</dl>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.array-key-first-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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Returns the first key of <code class="parameter">array</code> if the array is not empty;
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<strong><code>NULL</code></strong> otherwise.
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.array-key-first-examples">
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<h3 class="title">范例</h3>
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<p class="para">
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<div class="example" id="function.array-fill.example.basic">
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<p><strong>Example #1 Basic <span class="function"><strong>array_key_first()</strong></span> Usage</strong></p>
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<div class="example-contents">
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<div class="phpcode"><pre><span style="color: #000000">
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<span style="color: #0000BB"><?php<br />$array </span><span style="color: #007700">= [</span><span style="color: #DD0000">'a' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'b' </span><span style="color: #007700">=> </span><span style="color: #0000BB">2</span><span style="color: #007700">, </span><span style="color: #DD0000">'c' </span><span style="color: #007700">=> </span><span style="color: #0000BB">3</span><span style="color: #007700">];<br /><br /></span><span style="color: #0000BB">$firstKey </span><span style="color: #007700">= </span><span style="color: #0000BB">array_key_first</span><span style="color: #007700">(</span><span style="color: #0000BB">$array</span><span style="color: #007700">);<br /><br /></span><span style="color: #0000BB">var_dump</span><span style="color: #007700">(</span><span style="color: #0000BB">$firstKey</span><span style="color: #007700">);<br /></span><span style="color: #0000BB">?></span>
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</span>
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</pre></div>
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</div>
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<div class="example-contents"><p>以上例程会输出：</p></div>
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<div class="example-contents screen">
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<div class="cdata"><pre>
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string(1) "a"
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</pre></div>
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</div>
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</div>
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</p>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.array-key-first-seealso">
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<h3 class="title">参见</h3>
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="array_key_last.html" class="function" rel="rdfs-seeAlso">array_key_last()</a> - Gets the last key of an array</span></li>
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<li class="member"><span class="function"><a href="reset.html" class="function" rel="rdfs-seeAlso">reset()</a> - 将数组的内部指针指向第一个单元</span></li>
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</ul>
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</div>
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</div></div></div></body></html> |