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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xml:id="function.microtime" xmlns="http://docbook.org/ns/docbook">
<refnamediv>
<refname>microtime</refname>
<refpurpose>Return current Unix timestamp with microseconds</refpurpose>
</refnamediv>
<refsect1 role="description">
&reftitle.description;
<methodsynopsis>
<type class="union"><type>string</type><type>float</type></type><methodname>microtime</methodname>
<methodparam choice="opt"><type>bool</type><parameter>as_float</parameter><initializer>&false;</initializer></methodparam>
</methodsynopsis>
<para>
<function>microtime</function> returns the current Unix timestamp with
microseconds. This function is only available on operating systems that
support the gettimeofday() system call.
</para>
<para>
For performance measurements, using <function>hrtime</function> is recommended.
</para>
</refsect1>
<refsect1 role="parameters">
&reftitle.parameters;
<para>
<variablelist>
<varlistentry>
<term><parameter>as_float</parameter></term>
<listitem>
<para>
If used and set to &true;, <function>microtime</function> will return a
<type>float</type> instead of a <type>string</type>, as described in
the return values section below.
</para>
</listitem>
</varlistentry>
</variablelist>
</para>
</refsect1>
<refsect1 role="returnvalues">
&reftitle.returnvalues;
<para>
By default, <function>microtime</function> returns a <type>string</type> in
the form "msec sec", where <literal>sec</literal> is the number of seconds
since the Unix epoch (0:00:00 January 1,1970 GMT), and <literal>msec</literal>
measures microseconds that have elapsed since <literal>sec</literal>
and is also expressed in seconds as a decimal fraction.
</para>
<para>
If <parameter>as_float</parameter> is set to &true;, then
<function>microtime</function> returns a <type>float</type>, which
represents the current time in seconds since the Unix epoch accurate to the
nearest microsecond.
</para>
</refsect1>
<refsect1 role="examples">
&reftitle.examples;
<para>
<example>
<title>Timing script execution</title>
<programlisting role="php">
<![CDATA[
<?php
$time_start = microtime(true);
// Sleep for a while
usleep(100);
$time_end = microtime(true);
$time = $time_end - $time_start;
echo "Did nothing in $time seconds\n";
?>
]]>
</programlisting>
</example>
<example>
<title><function>microtime</function> and <literal>REQUEST_TIME_FLOAT</literal></title>
<programlisting role="php">
<![CDATA[
<?php
// Randomize sleeping time
usleep(mt_rand(100, 10000));
// REQUEST_TIME_FLOAT is available in the $_SERVER superglobal array.
// It contains the timestamp of the start of the request with microsecond precision.
$time = microtime(true) - $_SERVER["REQUEST_TIME_FLOAT"];
echo "Did nothing in $time seconds\n";
?>
]]>
</programlisting>
</example>
</para>
</refsect1>
<refsect1 role="seealso">
&reftitle.seealso;
<para>
<simplelist>
<member><function>time</function></member>
<member><function>hrtime</function></member>
</simplelist>
</para>
</refsect1>
</refentry>
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