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127 lines
3.6 KiB
XML
Executable File
127 lines
3.6 KiB
XML
Executable File
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: 3a8c3e77df070a046c9d5b56b68926ca2d7e5ee3 Maintainer: mowangjuanzi Status: ready -->
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<refentry xml:id="function.microtime" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>microtime</refname>
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<refpurpose>返回当前 Unix 时间戳和微秒数</refpurpose>
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</refnamediv>
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<refsect1 role="description">
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&reftitle.description;
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<methodsynopsis>
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<type class="union"><type>string</type><type>float</type></type><methodname>microtime</methodname>
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<methodparam choice="opt"><type>bool</type><parameter>as_float</parameter><initializer>&false;</initializer></methodparam>
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</methodsynopsis>
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<para>
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<function>microtime</function> 返回当前 Unix
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时间戳以及微秒数。本函数仅在支持 gettimeofday()
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系统调用的操作系统下可用。
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</para>
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<para>
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对于性能测量，建议使用 <function>hrtime</function>。
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</para>
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</refsect1>
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<refsect1 role="parameters">
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&reftitle.parameters;
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<para>
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<variablelist>
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<varlistentry>
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<term><parameter>as_float</parameter></term>
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<listitem>
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<para>
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如果使用并设置为 &true;，<function>microtime</function>
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将返回浮点数而不是字符串，具体查看下面的返回值相关描述。
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</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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</refsect1>
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<refsect1 role="returnvalues">
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&reftitle.returnvalues;
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<para>
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默认情况下，<function>microtime</function> 返回“msec sec”形式的 <type>string</type>，其中
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<literal>sec</literal> 是自 Unix 纪元（格林威治标准时间 1970 年 1 月 1 日
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0:00:00）以来的秒数，<literal>msec</literal> 是自 <literal>sec</literal>
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以来经过的微秒，表示为秒数的小数部分。
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</para>
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<para>
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如果 <parameter>as_float</parameter> 设置为 &true;，然后 <function>microtime</function>
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返回 <type>float</type>，表示自 Unix 纪元以来的当前时间，以秒为单位，精确到最接近的微秒。
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</para>
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</refsect1>
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<refsect1 role="examples">
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&reftitle.examples;
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<para>
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<example>
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<title>计时脚本执行时间</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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$time_start = microtime(true);
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// Sleep 一会
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usleep(10_000);
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$time_end = microtime(true);
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$time = $time_end - $time_start;
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print "Did nothing in $time seconds\n";
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?>
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]]>
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</programlisting>
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</example>
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<example>
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<title><function>microtime</function> 和 <literal>REQUEST_TIME_FLOAT</literal></title>
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<programlisting role="php" annotations="non-interactive">
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<![CDATA[
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<?php
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// 随机 sleep 时间
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usleep(random_int(10_000, 1_000_000));
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// 在 $_SERVER 超全局数组中 REQUEST_TIME_FLOAT 是有效的。
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// 包含请求开始的时间戳，精度为微秒。
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$time = microtime(true) - $_SERVER["REQUEST_TIME_FLOAT"];
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echo "Did nothing in $time seconds\n";
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]]>
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</programlisting>
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</example>
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</para>
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</refsect1>
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<refsect1 role="seealso">
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&reftitle.seealso;
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<para>
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<simplelist>
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<member><function>time</function></member>
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<member><function>hrtime</function></member>
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</simplelist>
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</para>
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</refsect1>
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</refentry>
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<!-- Keep this comment at the end of the file
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Local variables:
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mode: sgml
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sgml-omittag:t
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sgml-shorttag:t
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sgml-minimize-attributes:nil
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sgml-always-quote-attributes:t
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sgml-indent-step:1
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sgml-indent-data:t
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indent-tabs-mode:nil
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sgml-parent-document:nil
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sgml-default-dtd-file:"~/.phpdoc/manual.ced"
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sgml-exposed-tags:nil
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sgml-local-catalogs:nil
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sgml-local-ecat-files:nil
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End:
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vim600: syn=xml fen fdm=syntax fdl=2 si
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vim: et tw=78 syn=sgml
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vi: ts=1 sw=1
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-->
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