php-doc-en/reference/filesystem/functions/clearstatcache.xml

<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<refentry xmlns="http://docbook.org/ns/docbook" xml:id="function.clearstatcache">
 <refnamediv>
  <refname>clearstatcache</refname>
  <refpurpose>Clears file status cache</refpurpose>
 </refnamediv>
 
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>void</type><methodname>clearstatcache</methodname>
   <methodparam choice="opt"><type>bool</type><parameter>clear_realpath_cache</parameter><initializer>false</initializer></methodparam>
   <methodparam choice="opt"><type>string</type><parameter>filename</parameter></methodparam>
  </methodsynopsis>
  <para>
   When you use <function>stat</function>, <function>lstat</function>, or
   any of the other functions listed in the affected functions list (below),
   PHP caches the information those functions return in order to provide
   faster performance. However, in certain cases, you may want to clear the
   cached information. For instance, if the same file is being checked
   multiple times within a single script, and that file is in danger of
   being removed or changed during that script's operation, you may elect to
   clear the status cache.  In these cases, you can use the
   <function>clearstatcache</function> function to clear the information
   that PHP caches about a file.
  </para>
  <para>
   You should also note that PHP doesn't cache information about non-existent
   files. So, if you call <function>file_exists</function> on a file that
   doesn't exist, it will return &false; until you create the file. If you
   create the file, it will return &true; even if you then delete the file.
   However <function>unlink</function> clears the cache automatically.
  </para>
  <note>
   <para>
    This function caches information about specific filenames, so you only
    need to call <function>clearstatcache</function> if you are performing
    multiple operations on the same filename and require the information
    about that particular file to not be cached.
   </para>
  </note>
  <para>
   Affected functions include <function>stat</function>,
   <function>lstat</function>,
   <function>file_exists</function>,
   <function>is_writable</function>,
   <function>is_readable</function>,
   <function>is_executable</function>,
   <function>is_file</function>,
   <function>is_dir</function>,
   <function>is_link</function>,
   <function>filectime</function>,
   <function>fileatime</function>,
   <function>filemtime</function>,
   <function>fileinode</function>,
   <function>filegroup</function>,
   <function>fileowner</function>,
   <function>filesize</function>,
   <function>filetype</function>, and
   <function>fileperms</function>.
  </para>
 </refsect1>

 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>clear_realpath_cache</parameter></term>
     <listitem>
      <para>
       Whether to clear the realpath cache or not.
      </para>
     </listitem>
    </varlistentry>
    <varlistentry>
     <term><parameter>filename</parameter></term>
     <listitem>
      <para>
       Clear the realpath cache for a specific filename; only used if
       <parameter>clear_realpath_cache</parameter> is &true;.
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>

 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &return.void;
  </para>
 </refsect1>

 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>5.3.0</entry>
       <entry>
        Added optional <parameter>clear_realpath_cache</parameter> 
        and <parameter>filename</parameter> parameters.
       </entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>

 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title><function>clearstatcache</function> example</title>
    <programlisting role="php">
<![CDATA[
<?php
$file = 'output_log.txt';

function get_owner($file)
{
    $stat = stat($file);
    $user = posix_getpwuid($stat['uid']);
    return $user['name'];
}

$format = "UID @ %s: %s\n";

printf($format, date('r'), get_owner($file));

chown($file, 'ross');
printf($format, date('r'), get_owner($file));

clearstatcache();
printf($format, date('r'), get_owner($file));
?>
]]>
    </programlisting>
    &example.outputs.similar;
    <screen>
<![CDATA[
UID @ Sun, 12 Oct 2008 20:48:28 +0100: root
UID @ Sun, 12 Oct 2008 20:48:28 +0100: root
UID @ Sun, 12 Oct 2008 20:48:28 +0100: ross
]]>
    </screen>
   </example>
  </para>
 </refsect1>

</refentry>

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