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魔王卷子
144 lines
4.0 KiB
XML
144 lines
4.0 KiB
XML
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: b4989f5c1f052314ff2c36e9cc3d56b3a7a24e9b Maintainer: daijie Status: ready -->
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<!-- CREDITS: mowangjuanzi -->
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<refentry xml:id="function.headers-sent" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>headers_sent</refname>
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<refpurpose>检测消息头是否已经发送</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>bool</type><methodname>headers_sent</methodname>
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<methodparam choice="opt"><type>string</type><parameter role="reference">filename</parameter><initializer>&null;</initializer></methodparam>
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<methodparam choice="opt"><type>int</type><parameter role="reference">line</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<para>
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检测消息头是否已经发送。
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</para>
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<para>
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消息头已经发送时，就无法通过 <function>header</function>
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添加更多头字段。使用此函数起码可以防止收到跟消息头相关的错误。另一个解决方案是用<link
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linkend="ref.outcontrol">输出缓冲</link>。
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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>filename</parameter></term>
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<listitem>
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<para>
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若设置了可选参数 <parameter>filename</parameter> 和
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<parameter>line</parameter>，<function>headers_sent</function> 会把 PHP 文件名放在
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<parameter>filename</parameter> 变量里，输出开始的行号放在 <parameter>line</parameter> 变量里。
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</para>
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<note>
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<para>
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如果在执行 PHP 源文件之前已经开始输出（例如由于启动错误），则 <parameter>filename</parameter> 参数将被设置为空字符串。
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</para>
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</note>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>line</parameter></term>
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<listitem>
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<para>
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输出开始的行号。
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</para>
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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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消息头未发送时，<function>headers_sent</function> 返回 &false;，否则返回 &true;。
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</para>
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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>使用 <function>headers_sent</function> 的例子</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// 没有消息头就发送一个
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if (!headers_sent()) {
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header('Location: http://www.example.com/');
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exit;
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}
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// 使用 file 和 line 参数选项的例子
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// 注意 $filename 和 $linenum 用于下文中使用
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// 所以不要提前为它们赋值
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if (!headers_sent($filename, $linenum)) {
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header('Location: http://www.example.com/');
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exit;
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// 很有可能在这里触发错误
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} else {
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echo "Headers already sent in $filename on line $linenum\n" .
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"Cannot redirect, for now please click this <a " .
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"href=\"http://www.example.com\">link</a> instead\n";
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exit;
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}
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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="notes">
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&reftitle.notes;
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¬e.network.header.sapi;
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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><function>ob_start</function></member>
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<member><function>trigger_error</function></member>
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<member><function>headers_list</function></member>
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<member>
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<function>header</function> 中有更多相关细节的讨论。
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</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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