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https://github.com/sigmasternchen/php-doc-en
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git-svn-id: https://svn.php.net/repository/phpdoc/en/trunk@238860 c90b9560-bf6c-de11-be94-00142212c4b1
239 lines
7.2 KiB
XML
239 lines
7.2 KiB
XML
<?xml version="1.0" encoding="iso-8859-1"?>
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<!-- $Revision: 1.30 $ -->
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<refentry xml:id="function.mysql-real-escape-string" xmlns="http://docbook.org/ns/docbook">
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<refnamediv>
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<refname>mysql_real_escape_string</refname>
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<refpurpose>Escapes special characters in a string for use in a SQL statement</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>string</type><methodname>mysql_real_escape_string</methodname>
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<methodparam><type>string</type><parameter>unescaped_string</parameter></methodparam>
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<methodparam choice="opt"><type>resource</type><parameter>link_identifier</parameter></methodparam>
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</methodsynopsis>
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<para>
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Escapes special characters in the <parameter>unescaped_string</parameter>,
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taking into account the current character set of the connection so that it
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is safe to place it in a <function>mysql_query</function>. If binary data
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is to be inserted, this function must be used.
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</para>
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<para>
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<function>mysql_real_escape_string</function> calls MySQL's library function
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mysql_real_escape_string, which prepends backslashes to the following characters:
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<literal>\x00</literal>, <literal>\n</literal>,
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<literal>\r</literal>, <literal>\</literal>, <literal>'</literal>,
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<literal>"</literal> and <literal>\x1a</literal>.
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</para>
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<para>
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This function must always (with few exceptions) be used to make data
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safe before sending a query to MySQL.
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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>unescaped_string</parameter></term>
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<listitem>
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<para>
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The string that is to be escaped.
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</para>
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</listitem>
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</varlistentry>
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&mysql.linkid.description;
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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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Returns the escaped string, or &false; on error.
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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>Simple <function>mysql_real_escape_string</function> example</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// Connect
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$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password')
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OR die(mysql_error());
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// Query
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$query = sprintf("SELECT * FROM users WHERE user='%s' AND password='%s'",
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mysql_real_escape_string($user),
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mysql_real_escape_string($password));
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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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<para>
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<example>
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<title>An example SQL Injection Attack</title>
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<programlisting role="php">
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<![CDATA[
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<?php
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// Query database to check if there are any matching users
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$query = "SELECT * FROM users WHERE user='{$_POST['username']}' AND password='{$_POST['password']}'";
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mysql_query($query);
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// We didn't check $_POST['password'], it could be anything the user wanted! For example:
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$_POST['username'] = 'aidan';
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$_POST['password'] = "' OR ''='";
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// This means the query sent to MySQL would be:
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echo $query;
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?>
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]]>
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</programlisting>
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<para>
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The query sent to MySQL:
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</para>
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<screen>
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<![CDATA[
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SELECT * FROM users WHERE user='aidan' AND password='' OR ''=''
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]]>
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</screen>
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<para>
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This would allow anyone to log in without a valid password.
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</para>
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</example>
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</para>
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<para>
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<example>
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<title>A "Best Practice" query</title>
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<para>
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Using <function>mysql_real_escape_string</function> around each variable
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prevents SQL Injection. This example demonstrates the "best practice"
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method for querying a database, independent of the
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<link linkend="security.magicquotes">Magic Quotes</link> setting.
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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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if (isset($_POST['product_name']) && isset($_POST['product_description']) && isset($_POST['user_id'])) {
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// Connect
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$link = mysql_connect('mysql_host', 'mysql_user', 'mysql_password');
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if(!is_resource($link)) {
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echo "Failed to connect to the server\n";
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// ... log the error properly
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} else {
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// Reverse magic_quotes_gpc/magic_quotes_sybase effects on those vars if ON.
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if(get_magic_quotes_gpc()) {
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$product_name = stripslashes($_POST['product_name']);
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$product_description = stripslashes($_POST['product_description']);
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} else {
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$product_name = $_POST['product_name'];
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$product_description = $_POST['product_description'];
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}
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// Make a safe query
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$query = sprintf("INSERT INTO products (`name`, `description`, `user_id`) VALUES ('%s', '%s', %d)",
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mysql_real_escape_string($product_name, $link),
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mysql_real_escape_string($product_description, $link),
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$_POST['user_id']);
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mysql_query($query, $link);
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if (mysql_affected_rows($link) > 0) {
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echo "Product inserted\n";
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}
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}
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} else {
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echo "Fill the form properly\n";
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}
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?>
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]]>
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</programlisting>
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<para>
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The query will now execute correctly, and SQL Injection attacks will not work.
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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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<note>
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<para>
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A MySQL connection is required before using
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<function>mysql_real_escape_string</function> otherwise an error of
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level <literal>E_WARNING</literal> is generated, and &false; is
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returned. If <parameter>link_identifier</parameter> isn't defined, the
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last MySQL connection is used.
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</para>
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</note>
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<note>
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<para>
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If <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link> is enabled,
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first apply <function>stripslashes</function> to the data. Using this function
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on data which has already been escaped will escape the data twice.
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</para>
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</note>
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<note>
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<para>
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If this function is not used to escape data, the query is vulnerable to
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<link linkend="security.database.sql-injection">SQL Injection Attacks</link>.
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</para>
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</note>
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<note>
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<simpara>
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<function>mysql_real_escape_string</function> does not escape
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<literal>%</literal> and <literal>_</literal>. These are wildcards in
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MySQL if combined with <literal>LIKE</literal>, <literal>GRANT</literal>,
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or <literal>REVOKE</literal>.
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</simpara>
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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>mysql_client_encoding</function></member>
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<member><function>addslashes</function></member>
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<member><function>stripslashes</function></member>
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<member>The <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link> directive</member>
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<member>The <link linkend="ini.magic-quotes-runtime">magic_quotes_runtime</link> directive</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:"../../../../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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