php-doc-en/reference/datetime/functions/microtime.xml

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<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>mixed</type><methodname>microtime</methodname>
   <methodparam choice="opt"><type>bool</type><parameter>getAsFloat</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>getAsFloat</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.
  </para>
  <para>
   If <parameter>getAsFloat</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 with <function>microtime</function></title>
    <programlisting role="php">
<![CDATA[
<?php
/**
 * Simple function to replicate PHP 5 behaviour
 */
function microtime_float()
{
    list($usec, $sec) = explode(" ", microtime());
    return ((float)$usec + (float)$sec);
}

$time_start = microtime_float();

// Sleep for a while
usleep(100);

$time_end = microtime_float();
$time = $time_end - $time_start;

echo "Did nothing in $time seconds\n";
?>
]]>
    </programlisting>
   </example>
   <example>
    <title>Timing script execution in PHP 5</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> (as of PHP 5.4.0)</title>
    <programlisting role="php">
<![CDATA[
<?php
// Randomize sleeping time
usleep(mt_rand(100, 10000));

// As of PHP 5.4.0, 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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