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118 lines
6.1 KiB
HTML
118 lines
6.1 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>生成一个唯一ID</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.uniqid" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">uniqid</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">uniqid</span> — <span class="dc-title">生成一个唯一ID</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.uniqid-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>uniqid</strong></span>
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([ <span class="methodparam"><span class="type">string</span> <code class="parameter">$prefix</code><span class="initializer"> = ""</span></span>
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[, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$more_entropy</code><span class="initializer"> = false</span></span>
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]] ) : <span class="type">string</span></div>
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<p class="para rdfs-comment">
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获取一个带前缀、基于当前时间微秒数的唯一ID。
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</p>
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<div class="caution"><strong class="caution">Caution</strong><p class="para">本函数并不会生成安全加密的值，不应用于加密用途。若需要安全加密的值，考虑使用<span class="function"><a href="openssl_random_pseudo_bytes.html" class="function">openssl_random_pseudo_bytes()</a></span>。</p></div>
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<div class="warning"><strong class="warning">Warning</strong>
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<p class="para">
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此函数不保证返回值的唯一性。
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由于绝大多数系统使用 NTP 或者类似服务调整系统的时间，所以系统时间经常发生变化。
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此外，进程/线程可能不会返回唯一的 ID。
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用 <code class="parameter">more_entropy</code> 来增加唯一性的概率。
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</p>
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</div>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.uniqid-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">prefix</code></dt>
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<dd>
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<p class="para">
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有用的参数。例如：如果在多台主机上可能在同一微秒生成唯一ID。
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</p>
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<p class="para">
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<code class="parameter">prefix</code>为空，则返回的字符串长度为13。<code class="parameter">more_entropy</code> 为
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<strong><code>TRUE</code></strong>，则返回的字符串长度为23。
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</p>
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</dd>
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<dt>
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<code class="parameter">more_entropy</code></dt>
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<dd>
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<p class="para">
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如果设置为 <strong><code>TRUE</code></strong>，<span class="function"><strong>uniqid()</strong></span> 会在返回的字符串结尾增加额外的熵（使用combined linear congruential generator）。
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使得唯一ID更具唯一性。
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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.uniqid-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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返回字符串形式的唯一ID。
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</p>
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<div class="warning"><strong class="warning">Warning</strong>
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<p class="para">
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此函数努力创建唯一识别符，但它不保证返回值得唯一性。
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</p>
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</div>
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</div>
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<div class="refsect1 examples" id="refsect1-function.uniqid-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-4552">
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<p><strong>Example #1 <span class="function"><strong>uniqid()</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 /></span><span style="color: #FF8000">/* A uniqid, like: 4b3403665fea6 */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid(): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">());<br /><br /></span><span style="color: #FF8000">/* We can also prefix the uniqid, this the same as <br /> * doing:<br /> *<br /> * $uniqid = $prefix . uniqid();<br /> * $uniqid = uniqid($prefix);<br /> */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('php_'): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">(</span><span style="color: #DD0000">'php_'</span><span style="color: #007700">));<br /><br /></span><span style="color: #FF8000">/* We can also activate the more_entropy parameter, which is <br /> * required on some systems, like Cygwin. This makes uniqid()<br /> * produce a value like: 4b340550242239.64159797<br /> */<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('', true): %s\r\n"</span><span style="color: #007700">, </span><span style="color: #0000BB">uniqid</span><span style="color: #007700">(</span><span style="color: #DD0000">''</span><span style="color: #007700">, </span><span style="color: #0000BB">true</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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</p>
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</div>
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<div class="refsect1 notes" id="refsect1-function.uniqid-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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在Cygwin环境下，为了使此函数能够工作，<code class="parameter">more_entropy</code> 必须设置为 <strong><code>TRUE</code></strong>。
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</p>
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</p></blockquote>
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</div>
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</div></div></div></body></html> |