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130 lines
5.5 KiB
HTML
130 lines
5.5 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>播下一个更好的随机数发生器种子</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.mt-srand" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">mt_srand</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">mt_srand</span> — <span class="dc-title">播下一个更好的随机数发生器种子</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.mt-srand-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>mt_srand</strong></span>
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([ <span class="methodparam"><span class="type">int</span> <code class="parameter">$seed</code></span>
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] ) : <span class="type"><span class="type void">void</span></span></div>
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<p class="para rdfs-comment">
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用
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<code class="parameter">seed</code> 来给随机数发生器播种。 没有设定 <code class="parameter">seed</code> 参数时，会被设为随时数。
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</p>
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<blockquote class="note"><p><strong class="note">Note</strong>: <span class="simpara">自 PHP 4.2.0 起，不再需要用
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<span class="function"><a href="srand.html" class="function">srand()</a></span> 或 <span class="function"><strong>mt_srand()</strong></span>
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给随机数发生器播种 ，因为现在是由系统自动完成的。</span></p></blockquote>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.mt-srand-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">seed</code></dt>
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<dd>
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<p class="para">
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可选的种子值
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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.mt-srand-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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没有返回值。
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</p>
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</div>
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<div class="refsect1 changelog" id="refsect1-function.mt-srand-changelog">
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<h3 class="title">更新日志</h3>
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<p class="para">
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<table class="doctable informaltable">
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<thead>
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<tr>
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<th>版本</th>
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<th>说明</th>
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</tr>
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</thead>
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<tbody class="tbody">
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<tr>
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<td>4.2.0</td>
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<td>
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The <code class="parameter">seed</code> becomes optional
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and defaults to a random value if omitted.
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</td>
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</tr>
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<tr>
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<td>5.2.1</td>
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<td>
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The Mersenne Twister implementation in PHP now uses a new seeding
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algorithm by Richard Wagner. Identical seeds no longer produce the same
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sequence of values they did in previous versions. This behavior is not
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expected to change again, but it is considered unsafe to rely upon it
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nonetheless.
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</td>
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</tr>
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</tbody>
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</table>
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.mt-srand-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-4136">
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<p><strong>Example #1 <span class="function"><strong>mt_srand()</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">// seed with microseconds<br /></span><span style="color: #007700">function </span><span style="color: #0000BB">make_seed</span><span style="color: #007700">()<br />{<br /> list(</span><span style="color: #0000BB">$usec</span><span style="color: #007700">, </span><span style="color: #0000BB">$sec</span><span style="color: #007700">) = </span><span style="color: #0000BB">explode</span><span style="color: #007700">(</span><span style="color: #DD0000">' '</span><span style="color: #007700">, </span><span style="color: #0000BB">microtime</span><span style="color: #007700">());<br /> return (float) </span><span style="color: #0000BB">$sec </span><span style="color: #007700">+ ((float) </span><span style="color: #0000BB">$usec </span><span style="color: #007700">* </span><span style="color: #0000BB">100000</span><span style="color: #007700">);<br />}<br /></span><span style="color: #0000BB">mt_srand</span><span style="color: #007700">(</span><span style="color: #0000BB">make_seed</span><span style="color: #007700">());<br /></span><span style="color: #0000BB">$randval </span><span style="color: #007700">= </span><span style="color: #0000BB">mt_rand</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 seealso" id="refsect1-function.mt-srand-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="mt_rand.html" class="function" rel="rdfs-seeAlso">mt_rand()</a> - 生成更好的随机数</span></li>
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<li class="member"><span class="function"><a href="mt_getrandmax.html" class="function" rel="rdfs-seeAlso">mt_getrandmax()</a> - 显示随机数的最大可能值</span></li>
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<li class="member"><span class="function"><a href="srand.html" class="function" rel="rdfs-seeAlso">srand()</a> - 播下随机数发生器种子</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> |