mirror of
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git-svn-id: https://svn.php.net/repository/phpdoc/zh/trunk@327909 c90b9560-bf6c-de11-be94-00142212c4b1
355 lines
12 KiB
XML
Executable File
355 lines
12 KiB
XML
Executable File
<?xml version="1.0" encoding="utf-8"?>
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<!-- $Revision$ -->
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<!-- EN-Revision: ce8212a9d067d3871e97027c6e41f096151ee82e Maintainer: HonestQiao Status: ready -->
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<!-- Reviewed: no Maintainer: HonestQiao -->
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<refentry xml:id="function.extract" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>extract</refname>
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<refpurpose>从数组中将变量导入到当前的符号表</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>int</type><methodname>extract</methodname>
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<methodparam><type>array</type><parameter role="reference">var_array</parameter></methodparam>
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<methodparam choice="opt"><type>int</type><parameter>extract_type</parameter><initializer>EXTR_OVERWRITE</initializer></methodparam>
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<methodparam choice="opt"><type>string</type><parameter>prefix</parameter><initializer>&null;</initializer></methodparam>
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</methodsynopsis>
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<para>
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本函数用来将变量从数组中导入到当前的符号表中。
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</para>
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<para>
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检查每个键名看是否可以作为一个合法的变量名，同时也检查和符号表中已有的变量名的冲突。
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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>var_array</parameter></term>
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<listitem>
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<para>
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一个关联数组。此函数会将键名当作变量名，值作为变量的值。
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对每个键／值对都会在当前的符号表中建立变量，并受到
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<parameter>extract_type</parameter> 和 <parameter>prefix</parameter> 参数的影响。
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</para>
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<para>
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必须使用关联数组，数字索引的数组将不会产生结果，除非用了
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<constant>EXTR_PREFIX_ALL</constant> 或者 <constant>EXTR_PREFIX_INVALID</constant>。
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>extract_type</parameter></term>
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<listitem>
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<para>
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对待非法／数字和冲突的键名的方法将根据
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<parameter>extract_type</parameter> 参数决定。可以是以下值之一：
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<variablelist>
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<varlistentry>
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<term><constant>EXTR_OVERWRITE</constant></term>
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<listitem>
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<simpara>
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如果有冲突，覆盖已有的变量。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_SKIP</constant></term>
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<listitem>
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<simpara>
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如果有冲突，不覆盖已有的变量。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_PREFIX_SAME</constant></term>
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<listitem>
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<simpara>如果有冲突，在变量名前加上前缀 <parameter>prefix</parameter>。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_PREFIX_ALL</constant></term>
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<listitem>
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<simpara>
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给所有变量名加上前缀
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<parameter>prefix</parameter>。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_PREFIX_INVALID</constant></term>
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<listitem>
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<simpara>
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仅在非法／数字的变量名前加上前缀 <parameter>prefix</parameter>。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_IF_EXISTS</constant></term>
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<listitem>
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<simpara>
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仅在当前符号表中已有同名变量时，覆盖它们的值。其它的都不处理。
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举个例子，以下情况非常有用：定义一些有效变量，然后从 <varname>$_REQUEST</varname> 中仅导入这些已定义的变量。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_PREFIX_IF_EXISTS</constant></term>
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<listitem>
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<simpara>
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仅在当前符号表中已有同名变量时，建立附加了前缀的变量名，其它的都不处理。
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</simpara>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><constant>EXTR_REFS</constant></term>
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<listitem>
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<simpara>
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将变量作为引用提取。这有力地表明了导入的变量仍然引用了
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<parameter>var_array</parameter> 参数的值。可以单独使用这个标志或者在
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<parameter>extract_type</parameter> 中用 OR 与其它任何标志结合使用。
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</simpara>
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</listitem>
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</varlistentry>
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</variablelist>
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</para>
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<para>
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如果没有指定 <parameter>extract_type</parameter>，则被假定为 <constant>EXTR_OVERWRITE</constant>。
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</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>prefix</parameter></term>
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<listitem>
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<para>
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注意 <parameter>prefix</parameter> 仅在
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<parameter>extract_type</parameter> 的值是
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<constant>EXTR_PREFIX_SAME</constant>，<constant>EXTR_PREFIX_ALL</constant>，<constant>EXTR_PREFIX_INVALID</constant>
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或 <constant>EXTR_PREFIX_IF_EXISTS</constant>
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时需要。
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如果附加了前缀后的结果不是合法的变量名，将不会导入到符号表中。前缀和数组键名之间会自动加上一个下划线。
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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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返回成功导入到符号表中的变量数目。
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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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<para>
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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>4.3.0</entry>
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<entry>
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增加了 <constant>EXTR_REFS</constant>。
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</entry>
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</row>
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<row>
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<entry>4.2.0</entry>
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<entry>
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引进 <constant>EXTR_IF_EXISTS</constant> 和 <constant>EXTR_PREFIX_IF_EXISTS</constant> 。
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</entry>
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</row>
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<row>
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<entry>4.0.5</entry>
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<entry>
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函数可以返回被提取的变量数目。
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增加了 <constant>EXTR_PREFIX_INVALID</constant>。
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从这时起 <constant>EXTR_PREFIX_ALL</constant> 也包括了对数字索引的处理。
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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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</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><function>extract</function> 例子</title>
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<para>
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<function>extract</function> 的一种可能用法是将 <function>wddx_deserialize</function>
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返回的结合数组中的内容导入到符号表变量中去。
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</para>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* 假定 $var_array 是 wddx_deserialize 返回的数组*/
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$size = "large";
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$var_array = array("color" => "blue",
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"size" => "medium",
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"shape" => "sphere");
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extract($var_array, EXTR_PREFIX_SAME, "wddx");
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echo "$color, $size, $shape, $wddx_size\n";
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?>
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]]>
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</programlisting>
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&example.outputs;
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<screen>
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<![CDATA[
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blue, large, sphere, medium
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]]>
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</screen>
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<para>
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<varname>$size</varname> 没有被覆盖，因为指定了
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<constant>EXTR_PREFIX_SAME</constant>，这使得 <varname>$wddx_size</varname>
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被建立。如果指定了 <constant>EXTR_SKIP</constant>，则 <varname>$wddx_size</varname>
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也不会被建立。<constant>EXTR_OVERWRITE</constant> 将使 <varname>$size</varname>
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的值为“medium”，<constant>EXTR_PREFIX_ALL</constant> 将建立新变量
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<varname>$wddx_color</varname>，<varname>$wddx_size</varname> 和
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<varname>$wddx_shape</varname>。
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</para>
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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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<warning>
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<para>
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不要对不能信任的数据使用
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<function>extract</function>，例如用户的输入（<varname>$_GET</varname>， <varname>$_FILES</varname>，...）。如果这样做，举例说，要临时运行依赖于
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<link linkend="security.globals">register_globals</link>
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的老代码，要确保使用不会覆盖的
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<parameter>extract_type</parameter> 值，例如
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<constant>EXTR_SKIP</constant>，并且要留意应该按照 <link linkend="ini.variables-order">variables_order</link> 在 <link linkend="ini">&php.ini;</link> 里
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定义的顺序来提取。
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</para>
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</warning>
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<note>
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<para>
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If you
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have <link linkend="security.globals">register_globals</link>
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turned on and you use <function>extract</function>
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on <varname>$_FILES</varname> and
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specify <constant>EXTR_SKIP</constant>, you may be surprised at
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the results.
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</para>
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<warning>
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<para>
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This is not recommended practice and is only documented here for
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completeness. The use
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of <link linkend="security.globals">register_globals</link> is
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deprecated and calling <function>extract</function> on untrusted
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data such as <varname>$_FILES</varname> is, as noted above, a
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potential security risk. If you encounter this issue, it means
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that you are using at least two poor coding practices.
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</para>
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</warning>
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<programlisting role="php">
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<![CDATA[
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<?php
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/* Suppose that $testfile is the name of a file upload input
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and that register_globals is turned on. */
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var_dump($testfile);
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extract($_FILES, EXTR_SKIP);
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var_dump($testfile);
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var_dump($testfile['tmp_name']);
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?>
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]]>
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</programlisting>
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<simpara>
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You might expect to see something like the following:
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</simpara>
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<screen>
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<![CDATA[
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string(14) "/tmp/phpgCCPX8"
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array(5) {
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["name"]=>
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string(10) "somefile.txt"
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["type"]=>
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string(24) "application/octet-stream"
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["tmp_name"]=>
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string(14) "/tmp/phpgCCPX8"
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["error"]=>
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int(0)
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["size"]=>
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int(4208)
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}
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string(14) "/tmp/phpgCCPX8"
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]]>
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</screen>
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<simpara>
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However, you would instead see something like this:
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</simpara>
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<screen>
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<![CDATA[
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string(14) "/tmp/phpgCCPX8"
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string(14) "/tmp/phpgCCPX8"
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string(1) "/"
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]]>
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</screen>
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<para>
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This is due to the fact that
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since <link linkend="security.globals">register_globals</link> is
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turned on, <varname>$testfile</varname> already exists in the
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global scope when <function>extract</function> is called. And
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since <constant>EXTR_SKIP</constant> is
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specified, <varname>$testfile</varname> is not overwritten with
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the contents of the <constant>$_FILES</constant> array
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so <varname>$testfile</varname> remains a string.
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Because <link linkend="language.types.string.substr">strings may
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be accessed using array syntax</link> and the non-numeric string
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<literal>tmp_name</literal> is interpreted
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as <literal>0</literal>, PHP
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sees <varname>$testfile['tmp_name']</varname>
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as <varname>$testfile[0]</varname>.
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</para>
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</note>
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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>compact</function></member>
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<member><function>list</function></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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