pi.xml

<?xml version="1.0" encoding="utf-8"?>
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<refentry xml:id="function.pi" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>pi</refname>
  <refpurpose>得到圆周率值</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
   <methodsynopsis>
    <type>float</type><methodname>pi</methodname>
    <void/>
   </methodsynopsis>
  <simpara>
   返回圆周率的近似值。也可以使用 <constant>M_PI</constant> 常量，该常量产生与 <function>pi</function> 完全相同的结果。
  </simpara>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  &no.function.parameters;
 </refsect1>
 
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   圆周率（pi）的浮点近似值。
  </para>
 </refsect1>
 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>pi</function> 示例</title>
    <programlisting role="php">
<![CDATA[
<?php
echo pi(); // 3.1415926535898
echo M_PI; // 3.1415926535898
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>
  </refentry>

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