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170 lines
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170 lines
11 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>对浮点数进行四舍五入</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.round" class="refentry">
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<div class="refnamediv">
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<h1 class="refname">round</h1>
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<p class="verinfo">(PHP 4, PHP 5, PHP 7)</p><p class="refpurpose"><span class="refname">round</span> — <span class="dc-title">对浮点数进行四舍五入</span></p>
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</div>
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<div class="refsect1 description" id="refsect1-function.round-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>round</strong></span>
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( <span class="methodparam"><span class="type">float</span> <code class="parameter">$val</code></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$precision</code><span class="initializer"> = 0</span></span>
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[, <span class="methodparam"><span class="type">int</span> <code class="parameter">$mode</code><span class="initializer"> = PHP_ROUND_HALF_UP</span></span>
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]] ) : <span class="type">float</span></div>
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<p class="para rdfs-comment">
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返回将 <code class="parameter">val</code> 根据指定精度
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<code class="parameter">precision</code>（十进制小数点后数字的数目）进行四舍五入的结果。<code class="parameter">precision</code>
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也可以是负数或零（默认值）。
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</p>
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<p class="para">
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<blockquote class="note"><p><strong class="note">Note</strong>:
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<span class="simpara">
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PHP 默认不能正确处理类似 <em>"12,300.2"</em>
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的字符串。见<a href="language.types.string.html#language.types.string.conversion" class="link">字符串转换为数值</a>。
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</span>
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</p></blockquote>
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</p>
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</div>
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<div class="refsect1 parameters" id="refsect1-function.round-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">val</code></dt>
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<dd>
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<p class="para">
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要处理的值
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</p>
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</dd>
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<dt>
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<code class="parameter">precision</code></dt>
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<dd>
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<p class="para">
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可选的十进制小数点后数字的数目。
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</p>
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</dd>
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<dt>
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<code class="parameter">mode</code></dt>
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<dd>
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<p class="para">
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以下之一： <strong><code>PHP_ROUND_HALF_UP</code></strong>、
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<strong><code>PHP_ROUND_HALF_DOWN</code></strong>
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<strong><code>PHP_ROUND_HALF_EVEN</code></strong> 或
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<strong><code>PHP_ROUND_HALF_ODD</code></strong>
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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.round-returnvalues">
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<h3 class="title">返回值</h3>
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<p class="para">
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四舍五入后的值
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</p>
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</div>
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<div class="refsect1 examples" id="refsect1-function.round-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-4142">
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<p><strong>Example #1 <span class="function"><strong>round()</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: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">3.4</span><span style="color: #007700">); </span><span style="color: #FF8000">// 3<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">3.5</span><span style="color: #007700">); </span><span style="color: #FF8000">// 4<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">3.6</span><span style="color: #007700">); </span><span style="color: #FF8000">// 4<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">3.6</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">); </span><span style="color: #FF8000">// 4<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">1.95583</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1.96<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">1241757</span><span style="color: #007700">, -</span><span style="color: #0000BB">3</span><span style="color: #007700">); </span><span style="color: #FF8000">// 1242000<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">5.045</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">); </span><span style="color: #FF8000">// 5.05<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">5.055</span><span style="color: #007700">, </span><span style="color: #0000BB">2</span><span style="color: #007700">); </span><span style="color: #FF8000">// 5.06<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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<p class="para">
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<div class="example" id="example-4143">
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<p><strong>Example #2 <code class="parameter">mode</code> 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: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">9.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_UP</span><span style="color: #007700">); </span><span style="color: #FF8000">// 10<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">9.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_DOWN</span><span style="color: #007700">); </span><span style="color: #FF8000">// 9<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">9.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_EVEN</span><span style="color: #007700">); </span><span style="color: #FF8000">// 10<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">9.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_ODD</span><span style="color: #007700">); </span><span style="color: #FF8000">// 9<br /><br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">8.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_UP</span><span style="color: #007700">); </span><span style="color: #FF8000">// 9<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">8.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_DOWN</span><span style="color: #007700">); </span><span style="color: #FF8000">// 8<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">8.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_EVEN</span><span style="color: #007700">); </span><span style="color: #FF8000">// 8<br /></span><span style="color: #007700">echo </span><span style="color: #0000BB">round</span><span style="color: #007700">(</span><span style="color: #0000BB">8.5</span><span style="color: #007700">, </span><span style="color: #0000BB">0</span><span style="color: #007700">, </span><span style="color: #0000BB">PHP_ROUND_HALF_ODD</span><span style="color: #007700">); </span><span style="color: #FF8000">// 9<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 changelog" id="refsect1-function.round-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>5.3.0</td>
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<td>
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引入了 <code class="parameter">mode</code> 参数
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</td>
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</tr>
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<tr>
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<td>5.2.7</td>
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<td>
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<span class="function"><strong>round()</strong></span> 的内部运作修改符合 C99 的标准。
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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 seealso" id="refsect1-function.round-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="ceil.html" class="function" rel="rdfs-seeAlso">ceil()</a> - 进一法取整</span></li>
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<li class="member"><span class="function"><a href="floor.html" class="function" rel="rdfs-seeAlso">floor()</a> - 舍去法取整</span></li>
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<li class="member"><span class="function"><a href="number_format.html" class="function" rel="rdfs-seeAlso">number_format()</a> - 以千位分隔符方式格式化一个数字</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> |