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  5.   <title>生成一个唯一ID</title>
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  13. </div><hr /><div id="function.uniqid" class="refentry">
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  14.  <div class="refnamediv">
    15. 

  15.   <h1 class="refname">uniqid</h1>
    16. 

  16.   <p class="verinfo">(PHP 4, PHP 5)</p><p class="refpurpose"><span class="refname">uniqid</span> &mdash; <span class="dc-title">生成一个唯一ID</span></p>
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  17. 

  18.  </div>
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  19.  
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  20.  <div class="refsect1 description" id="refsect1-function.uniqid-description">
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  21.   <h3 class="title">说明</h3>
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  22.   <div class="methodsynopsis dc-description">
    23. 

  23.    <span class="type">string</span> <span class="methodname"><strong>uniqid</strong></span>
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  24.     ([ <span class="methodparam"><span class="type">string</span> <code class="parameter">$prefix</code><span class="initializer"> = &quot;&quot;</span></span>
    25. 

  25.    [, <span class="methodparam"><span class="type">bool</span> <code class="parameter">$more_entropy</code><span class="initializer"> = false</span></span>
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  26.   ]] )</div>
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  27. 

  28.   <p class="para rdfs-comment">
    29. 

  29.    获取一个带前缀、基于当前时间微秒数的唯一ID。
    30. 

  30.   </p>
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  31.  </div>
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  32. 

  33. 

  34.  <div class="refsect1 parameters" id="refsect1-function.uniqid-parameters">
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  35.   <h3 class="title">参数</h3>
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  36.   <p class="para">
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  37.    <dl>
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  38. 

  39.     <dt>
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  40. 

  41.      <span class="term"><em><code class="parameter">prefix</code></em></span>
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  42.      <dd>
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  43. 

  44.       <p class="para">
    45. 

  45.        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。
    46. 

  46.       </p>
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  47.       <p class="para">
    48. 

  48.        <em><code class="parameter">prefix</code></em>为空，则返回的字符串长度为13。<em><code class="parameter">more_entropy</code></em> 为
    49. 

  49.        <strong><code>TRUE</code></strong>，则返回的字符串长度为23。
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  50.       </p>
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  51.      </dd>
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  52. 

  53.     </dt>
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  54. 

  55.     <dt>
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  56. 

  57.      <span class="term"><em><code class="parameter">more_entropy</code></em></span>
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  58.      <dd>
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  59. 

  60.       <p class="para">
    61. 

  61.        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煽（使用combined linear congruential generator）。
    62. 

  62.        使得唯一ID更具唯一性。
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  63.       </p>
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  64.      </dd>
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  65. 

  66.     </dt>
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  67. 

  68.    </dl>
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  69. 

  70.   </p>
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  71.  </div>
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  72. 

  73. 

  74.  <div class="refsect1 returnvalues" id="refsect1-function.uniqid-returnvalues">
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  75.   <h3 class="title">返回值</h3>
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  76.   <p class="para">
    77. 

  77.    返回字符串形式的唯一ID。
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  78.   </p>
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  79.  </div>
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  80. 

  81. 

  82.  <div class="refsect1 examples" id="refsect1-function.uniqid-examples">
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  83.   <h3 class="title">范例</h3>
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  84.   <p class="para">
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  85.    <div class="example" id="example-3579">
    86. 

  86.     <p><strong>Example #1  <span class="function"><strong>uniqid()</strong></span> 例子</strong></p>
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  87.     <div class="example-contents">
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  88. <div class="phpcode"><code><span style="color: #000000">
    89. 

  89. <span style="color: #0000BB">&lt;?php<br /></span><span style="color: #FF8000">/*&nbsp;A&nbsp;uniqid,&nbsp;like:&nbsp;4b3403665fea6&nbsp;*/<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid():&nbsp;%s\r\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">uniqid</span><span style="color: #007700">());<br /><br /></span><span style="color: #FF8000">/*&nbsp;We&nbsp;can&nbsp;also&nbsp;prefix&nbsp;the&nbsp;uniqid,&nbsp;this&nbsp;the&nbsp;same&nbsp;as&nbsp;<br />&nbsp;*&nbsp;doing:<br />&nbsp;*<br />&nbsp;*&nbsp;$uniqid&nbsp;=&nbsp;$prefix&nbsp;.&nbsp;uniqid();<br />&nbsp;*&nbsp;$uniqid&nbsp;=&nbsp;uniqid($prefix);<br />&nbsp;*/<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('php_'):&nbsp;%s\r\n"</span><span style="color: #007700">,&nbsp;</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">/*&nbsp;We&nbsp;can&nbsp;also&nbsp;activate&nbsp;the&nbsp;more_entropy&nbsp;parameter,&nbsp;which&nbsp;is&nbsp;<br />&nbsp;*&nbsp;required&nbsp;on&nbsp;some&nbsp;systems,&nbsp;like&nbsp;Cygwin.&nbsp;This&nbsp;makes&nbsp;uniqid()<br />&nbsp;*&nbsp;produce&nbsp;a&nbsp;value&nbsp;like:&nbsp;4b340550242239.64159797<br />&nbsp;*/<br /></span><span style="color: #0000BB">printf</span><span style="color: #007700">(</span><span style="color: #DD0000">"uniqid('',&nbsp;true):&nbsp;%s\r\n"</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">uniqid</span><span style="color: #007700">(</span><span style="color: #DD0000">''</span><span style="color: #007700">,&nbsp;</span><span style="color: #0000BB">true</span><span style="color: #007700">));<br /></span><span style="color: #0000BB">?&gt;</span>
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  90. </span>
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  91. </code></div>
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  92.     </div>
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  93. 

  94.    </div>
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  95.   </p>
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  96.  </div>
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  97. 

  98. 

  99.  <div class="refsect1 changelog" id="refsect1-function.uniqid-changelog">
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  100.   <h3 class="title">更新日志</h3>
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  101.   <p class="para">
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  102.    <table class="doctable informaltable">
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  103.     
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  104.      <thead>
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  105.       <tr>
    106. 

  106.        <th>版本</th>
    107. 

  107.        <th>说明</th>
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  108.       </tr>
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  109. 

  110.      </thead>
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  111. 

  112.      <tbody class="tbody">
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  113.       <tr>
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  114.        <td>5.0.0</td>
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  115.        <td>
    116. 

  116.         <em><code class="parameter">prefix</code></em> 参数设为可选。
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  117.        </td>
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  118.       </tr>
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  119. 

  120.       <tr>
    121. 

  121.        <td>4.3.1</td>
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  122.        <td>
    123. 

  123.         <em><code class="parameter">prefix</code></em> 参数的长度限制提升到114个字符。
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  124.        </td>
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  125.       </tr>
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  126. 

  127.      </tbody>
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  128.     
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  129.    </table>
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  130. 

  131.   </p>
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  132.  </div>
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  133. 

  134. 

  135.  <div class="refsect1 notes" id="refsect1-function.uniqid-notes">
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  136.   <h3 class="title">注释</h3>
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  137.   <blockquote class="note"><p><strong class="note">Note</strong>: 
    138. 

  138.    <p class="para">
    139. 

  139.     在Cygwin环境下，为了使此函数能够工作，<em><code class="parameter">more_entropy</code></em> 必须设置为 <strong><code>TRUE</code></strong>。
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  140.    </p>
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  141.   </p></blockquote>
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