<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- Generated by xml_proto.php v2.4. Found in /scripts directory of phpdoc. -->
<refentry xml:id="function.http-cache-last-modified" xmlns="http://docbook.org/ns/docbook">
 <refnamediv>
  <refname>http_cache_last_modified</refname>
  <refpurpose>Caching by last modification</refpurpose>
 </refnamediv>
 <refsect1 role="description">
  &reftitle.description;
  <methodsynopsis>
   <type>bool</type><methodname>http_cache_last_modified</methodname>
   <methodparam choice="opt"><type>int</type><parameter>timestamp_or_expires</parameter></methodparam>
  </methodsynopsis>
  <para>
   Attempts to cache the sent entity by its last modification date.
  </para>
  <para>
   If the supplied argument is greater than 0, it is handled as timestamp
   and will be sent as date of last modification. If it is 0 or omitted,
   the current time will be sent as <literal>Last-Modified</literal> date.
   If it's negative, it is handled as expiration time in seconds, which means 
   that if the requested last modification date is not between the calculated timespan,
   the <literal>Last-Modified</literal> header is updated and the actual body will be sent.
  </para>
  <para>
   A log entry will be written to the cache log if the &link.http.configuration;
   <link linkend="http.configuration.log.cache">http.log.cache</link> is set
   and the cache attempt was successful.
  </para>
  &note.http.send.API.mayuse;
 </refsect1>
 <refsect1 role="parameters">
  &reftitle.parameters;
  <para>
   <variablelist>
    <varlistentry>
     <term><parameter>timestamp_or_expires</parameter></term>
     <listitem>
      <para>
       Unix timestamp
      </para>
     </listitem>
    </varlistentry>
   </variablelist>
  </para>
 </refsect1>
 <refsect1 role="returnvalues">
  &reftitle.returnvalues;
  <para>
   &returns.http.false.orexits; with <literal>304 Not Modified</literal> if the entity is cached.
   &see.http.configuration.force_exit;
  </para>
 </refsect1>

 <!-- Use when ERRORS exist
 <refsect1 role="errors">
  &reftitle.errors;
  <para>
   When does this function throw E_* level errors, or exceptions?
  </para>
 </refsect1>
 -->


 <!-- Use when a CHANGELOG exists
 <refsect1 role="changelog">
  &reftitle.changelog;
  <para>
   <informaltable>
    <tgroup cols="2">
     <thead>
      <row>
       <entry>&Version;</entry>
       <entry>&Description;</entry>
      </row>
     </thead>
     <tbody>
      <row>
       <entry>Enter the PHP version of change here</entry>
       <entry>Description of change</entry>
      </row>
     </tbody>
    </tgroup>
   </informaltable>
  </para>
 </refsect1>
 -->


 <refsect1 role="examples">
  &reftitle.examples;
  <para>
   <example>
    <title>A <function>http_cache_last_modified</function> example</title>
    <para>
     Caching for 5 seconds.
    </para>
    <programlisting role="php">
<![CDATA[
<?php
http_cache_last_modified(-5);
printf("%s\n", http_date());
?>
]]>
    </programlisting>
   </example>
  </para>
 </refsect1>


 <refsect1 role="seealso">
  &reftitle.seealso;
  <para>
   <simplelist>
    <member><function>http_cache_etag</function></member>
    <member>&http.response.class.php51;</member>
   </simplelist>
  </para>
 </refsect1>


</refentry>

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