mirror of
https://github.com/php/doc-zh.git
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Luffy
207 lines
6.0 KiB
XML
207 lines
6.0 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: 1cef066aa4ecd6691264701d0b6d7814230fa37c Maintainer: yuanyuqiang Status: ready -->
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<!-- CREDITS: mowangjuanzi, Luffy -->
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<refentry xml:id="function.session-cache-limiter" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>session_cache_limiter</refname>
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<refpurpose>读取/设置缓存限制器</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>false</type></type><methodname>session_value</methodname>
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<methodparam choice="opt"><type class="union"><type>string</type><type>null</type></type><parameter>value</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<para>
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<function>session_cache_limiter</function> 返回当前缓存限制器的名称。
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</para>
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<para>
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缓存限制器定义了向客户端发送的 HTTP 响应头中的缓存控制策略。
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客户端或者代理服务器通过检测这个响应头信息来
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确定对于页面内容的缓存规则。
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设置缓存限制器为 <literal>nocache</literal> 会禁止客户端或者代理服务器缓存内容，
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<literal>public</literal> 表示允许客户端或代理服务器缓存内容，
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<literal>private</literal> 表示允许客户端缓存，
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但是不允许代理服务器缓存内容。
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</para>
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<para>
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在 <literal>private</literal> 模式下， 包括 <productname>Mozilla</productname>
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在内的一些浏览器可能无法正确处理 Expire 响应头，
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通过使用 <literal>private_no_expire</literal> 模式可以解决这个问题：在这种模式下，
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不会向客户端发送 <literal>Expire</literal> 响应头。
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</para>
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<para>
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设置为 <literal>''</literal> 可以关闭
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自动发送缓存策略响应头的功能。
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</para>
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<para>
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请求开始的时候，缓存限制器会被重置为默认值，并且存储在
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<link linkend="ini.session.cache-limiter">session.cache_limiter</link>
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配置项中。
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因此，如果要设置缓存限制器，对于每个请求，
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都需要在调用 <function>session_start</function> 函数之前，
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调用 <function>session_cache_limiter</function> 函数来进行设置。
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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>value</parameter></term>
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<listitem>
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<para>
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如果指定 <parameter>value</parameter> 且不为 &null;，
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将使用指定值作为缓存限制器的值。
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</para>
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<table>
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<title>可选的值</title>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>值</entry>
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<entry>发送的响应头</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry><literal>public</literal></entry>
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<entry>
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<programlisting role="header">
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<![CDATA[
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Expires: (sometime in the future, according session.cache_expire)
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Cache-Control: public, max-age=(sometime in the future, according to session.cache_expire)
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Last-Modified: (the timestamp of the current script)
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]]>
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</programlisting>
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</entry>
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</row>
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<row>
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<entry><literal>private_no_expire</literal></entry>
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<entry>
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<programlisting role="header">
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<![CDATA[
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Cache-Control: private, max-age=(session.cache_expire in the future)
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Last-Modified: (the timestamp of the current script)
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]]>
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</programlisting>
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</entry>
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</row>
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<row>
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<entry><literal>private</literal></entry>
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<entry>
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<programlisting role="header">
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<![CDATA[
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Expires: Thu, 19 Nov 1981 08:52:00 GMT
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Cache-Control: private, max-age=(session.cache_expire in the future)
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Last-Modified: (the timestamp of the current script)
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]]>
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</programlisting>
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</entry>
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</row>
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<row>
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<entry><literal>nocache</literal></entry>
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<entry>
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<programlisting role="header">
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<![CDATA[
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Expires: Thu, 19 Nov 1981 08:52:00 GMT
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Cache-Control: no-store, no-cache, must-revalidate
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Pragma: no-cache
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]]>
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</programlisting>
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</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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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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返回当前所用的缓存限制器名称。如果更改值失败，则返回 &false;。
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</para>
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</refsect1>
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<refsect1 role="changelog">
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&reftitle.changelog;
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<informaltable>
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<tgroup cols="2">
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<thead>
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<row>
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<entry>&Version;</entry>
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<entry>&Description;</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>8.0.0</entry>
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<entry>
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<parameter>value</parameter> 现在可为 null。
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</entry>
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</row>
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</tbody>
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</tgroup>
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</informaltable>
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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><function>session_cache_limiter</function> 示例</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* 设置缓存限制器为 'private' */
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session_cache_limiter('private');
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$cache_limiter = session_cache_limiter();
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echo "The cache limiter is now set to $cache_limiter<br />";
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?>
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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><link linkend="ini.session.cache-limiter">session.cache_limiter</link></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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