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141 lines
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HTML
141 lines
7.9 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>检查数组里是否有指定的键名或索引</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-exists" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">array_key_exists</h1>
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<p class="verinfo">(PHP 4 >= 4.0.7, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">array_key_exists</span> — <span class="dc-title">检查数组里是否有指定的键名或索引</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.array-key-exists-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_exists</strong></span>
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( <span class="methodparam"><span class="type"><a href="language.pseudo-types.html#language.types.mixed" class="type mixed">mixed</a></span> <code class="parameter">$key</code></span>
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, <span class="methodparam"><span class="type">array</span> <code class="parameter">$array</code></span>
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) : <span class="type">bool</span></div>
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<p class="para rdfs-comment">
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数组里有键 <code class="parameter">key</code> 时，<span class="function"><strong>array_key_exists()</strong></span> 返回 <strong><code>TRUE</code></strong>。
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<code class="parameter">key</code>
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可以是任何能作为数组索引的值。
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.array-key-exists-parameters">
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<h3 class="title">参数</h3>
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<p class="para">
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<dl>
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<dt>
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<code class="parameter">key</code></dt>
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<dd>
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<p class="para">
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要检查的键。
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</p>
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</dd>
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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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一个数组，包含待检查的键。
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</p>
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</dd>
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</dl>
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</p>
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</div>
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<div class="refsect1 returnvalues" id="refsect1-function.array-key-exists-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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成功时返回 <strong><code>TRUE</code></strong>， 或者在失败时返回 <strong><code>FALSE</code></strong>。
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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<span class="function"><strong>array_key_exists()</strong></span> 仅仅搜索第一维的键。
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多维数组里嵌套的键不会被搜索到。
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 examples" id="refsect1-function.array-key-exists-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="example-6037">
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<p><strong>Example #1 <span class="function"><strong>array_key_exists()</strong></span> 例子</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 />$search_array </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'first' </span><span style="color: #007700">=> </span><span style="color: #0000BB">1</span><span style="color: #007700">, </span><span style="color: #DD0000">'second' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">);<br />if (</span><span style="color: #0000BB">array_key_exists</span><span style="color: #007700">(</span><span style="color: #DD0000">'first'</span><span style="color: #007700">, </span><span style="color: #0000BB">$search_array</span><span style="color: #007700">)) {<br /> echo </span><span style="color: #DD0000">"The 'first' element is in the array"</span><span style="color: #007700">;<br />}<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>
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</p>
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<div class="example" id="example-6038">
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<p><strong>Example #2 <span class="function"><strong>array_key_exists()</strong></span> 与 <span class="function"><a href="isset.html" class="function">isset()</a></span> 的对比</strong></p>
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<div class="example-contents"><p>
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<span class="function"><a href="isset.html" class="function">isset()</a></span> 对于数组中为 <strong><code>NULL</code></strong>
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的值不会返回 <strong><code>TRUE</code></strong>，而
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<span class="function"><strong>array_key_exists()</strong></span> 会。
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</p></div>
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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 />$search_array </span><span style="color: #007700">= array(</span><span style="color: #DD0000">'first' </span><span style="color: #007700">=> </span><span style="color: #0000BB">null</span><span style="color: #007700">, </span><span style="color: #DD0000">'second' </span><span style="color: #007700">=> </span><span style="color: #0000BB">4</span><span style="color: #007700">);<br /><br /></span><span style="color: #FF8000">// returns false<br /></span><span style="color: #007700">isset(</span><span style="color: #0000BB">$search_array</span><span style="color: #007700">[</span><span style="color: #DD0000">'first'</span><span style="color: #007700">]);<br /><br /></span><span style="color: #FF8000">// returns true<br /></span><span style="color: #0000BB">array_key_exists</span><span style="color: #007700">(</span><span style="color: #DD0000">'first'</span><span style="color: #007700">, </span><span style="color: #0000BB">$search_array</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>
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</div>
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<div class="refsect1 notes" id="refsect1-function.array-key-exists-notes">
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<h3 class="title">注释</h3>
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<p class="para">
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由于为了兼容以前版本，如果 <span class="type"><a href="language.types.object.html" class="type object">object</a></span> 当做 <code class="parameter">array</code> 传入 <span class="function"><strong>array_key_exists()</strong></span>，同时 <code class="parameter">key</code> 是对象的属性，也会返回 <strong><code>TRUE</code></strong>。
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不要依赖这个特性，保证参数 <code class="parameter">array</code> 类型是数组（<span class="type"><a href="language.types.array.html" class="type array">array</a></span>）。
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</p>
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<p class="para">
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要检查对象是否有某个属性，应该去用
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<span class="function"><a href="property_exists.html" class="function">property_exists()</a></span>。
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</p>
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</p></blockquote>
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</div>
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<div class="refsect1 seealso" id="refsect1-function.array-key-exists-seealso">
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<h3 class="title">参见</h3>
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<p class="para">
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<ul class="simplelist">
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<li class="member"><span class="function"><a href="isset.html" class="function" rel="rdfs-seeAlso">isset()</a> - 检测变量是否已设置并且非 NULL</span></li>
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<li class="member"><span class="function"><a href="array_keys.html" class="function" rel="rdfs-seeAlso">array_keys()</a> - 返回数组中部分的或所有的键名</span></li>
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<li class="member"><span class="function"><a href="in_array.html" class="function" rel="rdfs-seeAlso">in_array()</a> - 检查数组中是否存在某个值</span></li>
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<li class="member"><span class="function"><a href="property_exists.html" class="function" rel="rdfs-seeAlso">property_exists()</a> - 检查对象或类是否具有该属性</span></li>
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</ul>
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</p>
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</div>
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</div></div></div></body></html> |