php-doc-en/security/magicquotes.xml

<?xml version="1.0" encoding="iso-8859-1"?>
<!-- $Revision: 1.11 $ -->
  <chapter xml:id="security.magicquotes" xmlns="http://docbook.org/ns/docbook">
   <title>Magic Quotes</title>
   &warn.deprecated.feature-5-3-0.removed-6-0-0;
   <para>
    Magic Quotes is a process that automagically escapes incoming data to the 
    PHP script. It's preferred to code with magic quotes off and to instead
    escape the data at runtime, as needed.
   </para>

   <sect1 xml:id="security.magicquotes.what">
    <title>What are Magic Quotes</title>
    <para>
     When on, all <literal>'</literal> (single-quote), <literal>"</literal> 
     (double quote), <literal>\</literal> (backslash) and <literal>NULL</literal> 
     characters are escaped with a backslash automatically.  This is identical
     to what <function>addslashes</function> does.
    </para>
    <para>
     There are three magic quote directives:
    </para>
    <itemizedlist>
     <listitem>
      <simpara>
       <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>
      </simpara>
      <simpara>
       Affects HTTP Request data (GET, POST, and COOKIE). Cannot be set at 
       runtime, and defaults to <emphasis>on</emphasis> in PHP.
      </simpara>
      <simpara>
       See also <function>get_magic_quotes_gpc</function>.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       <link linkend="ini.magic-quotes-runtime">magic_quotes_runtime</link>
      </simpara>
      <simpara>
       If enabled, most functions that return data from an external source, 
       including databases and text files, will have quotes escaped with a 
       backslash. Can be set at runtime, and defaults to <emphasis>off</emphasis>
       in PHP.
      </simpara>
      <simpara>
       See also <function>set_magic_quotes_runtime</function> and
       <function>get_magic_quotes_runtime</function>.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       <link linkend="ini.magic-quotes-sybase">magic_quotes_sybase</link>
      </simpara>
      <simpara>
       If enabled, a single-quote is escaped with a single-quote instead of a 
       backslash.  If on, it completely overrides 
       <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>. Having 
       both directives enabled means only single quotes are escaped as 
       <literal>''</literal>. Double quotes, backslashes and NULL's will 
       remain untouched and unescaped.
      </simpara>
      <simpara>
       See also <function>ini_get</function> for retrieving its value.
      </simpara>
     </listitem>
    </itemizedlist>
   </sect1>

   <sect1 xml:id="security.magicquotes.why">
    <title>Why use Magic Quotes</title>
    <itemizedlist>
     <listitem>
      <simpara>
       Useful for beginners
      </simpara>
      <simpara>
       Magic quotes are implemented in PHP to help code written by beginners 
       from being dangerous. Although 
       <link linkend="security.database.sql-injection">SQL Injection</link> 
       is still possible with magic quotes on, the risk is reduced.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       Convenience
      </simpara>
      <simpara>
       For inserting data into a database, magic quotes essentially runs 
       <function>addslashes</function> on all Get, Post, and Cookie data,
       and does so automagically.
      </simpara>
     </listitem>
    </itemizedlist>
   </sect1>

   <sect1 xml:id="security.magicquotes.whynot">
    <title>Why not to use Magic Quotes</title>
    <itemizedlist>
     <listitem>
      <simpara>
       Portability
      </simpara>
      <simpara>
       Assuming it to be on, or off, affects portability. Use
       <function>get_magic_quotes_gpc</function> to check for this, and code
       accordingly.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       Performance
      </simpara>
      <simpara>
       Because not every piece of escaped data is inserted into a 
       database, there is a performance loss for escaping all this data. 
       Simply calling on the escaping functions (like 
       <function>addslashes</function>) at runtime is more efficient.
      </simpara>
      <simpara>
       Although <filename>php.ini-dist</filename> enables these directives  
       by default, <filename>php.ini-recommended</filename> disables it.
       This recommendation is mainly due to performance reasons.
      </simpara>
     </listitem>
     <listitem>
      <simpara>
       Inconvenience
      </simpara>
      <simpara>
       Because not all data needs escaping, it's often annoying to see escaped
       data where it shouldn't be. For example, emailing from a form, and
       seeing a bunch of \' within the email. To fix, this may require 
       excessive use of <function>stripslashes</function>.
      </simpara>
     </listitem>
    </itemizedlist>
   </sect1>

   <sect1 xml:id="security.magicquotes.disabling">
    <title>Disabling Magic Quotes</title>
    <para>
     The <link linkend="ini.magic-quotes-gpc">magic_quotes_gpc</link>
     directive may only be disabled at the system level, and not at
     runtime. In otherwords, use of <function>ini_set</function> is not
     an option.
    </para>
    <para>
     <example>
      <title>Disabling magic quotes server side</title>
      <para>
       An example that sets the value of these directives to 
       <literal>Off</literal> in &php.ini;.  For additional details, read the 
       manual section titled <link linkend="configuration.changes">How to 
       change configuration settings</link>.
      </para>
      <screen>
<![CDATA[
; Magic quotes
;

; Magic quotes for incoming GET/POST/Cookie data.
magic_quotes_gpc = Off

; Magic quotes for runtime-generated data, e.g. data from SQL, from exec(), etc.
magic_quotes_runtime = Off

; Use Sybase-style magic quotes (escape ' with '' instead of \').
magic_quotes_sybase = Off
]]>
      </screen>
      <para>
       If access to the server configuration is unavailable, use of
       <filename>.htaccess</filename> is also an option.  For example:
      </para>
      <screen>
<![CDATA[
php_flag magic_quotes_gpc Off
]]>
      </screen>
     </example>
    </para>
    <para>
     In the interest of writing portable code (code that works in any 
     environment), like if setting at the server level is not possible,
     here's an example to disable <link linkend="ini.magic-quotes-gpc">
     magic_quotes_gpc</link> at runtime. This method is inefficient so 
     it's preferred to instead set the appropriate directives elsewhere.
    </para>
    <para>
     <example>
      <title>Disabling magic quotes at runtime</title>
      <programlisting role="php">
<![CDATA[
<?php
if (get_magic_quotes_gpc()) {
    function stripslashes_deep($value)
    {
        $value = is_array($value) ?
                    array_map('stripslashes_deep', $value) :
                    stripslashes($value);

        return $value;
    }

    $_POST = array_map('stripslashes_deep', $_POST);
    $_GET = array_map('stripslashes_deep', $_GET);
    $_COOKIE = array_map('stripslashes_deep', $_COOKIE);
    $_REQUEST = array_map('stripslashes_deep', $_REQUEST);
}
?>
]]>
      </programlisting>
     </example>
    </para>
   </sect1>

  </chapter>

<!-- Keep this comment at the end of the file
Local variables:
mode: sgml
sgml-omittag:t
sgml-shorttag:t
sgml-minimize-attributes:nil
sgml-always-quote-attributes:t
sgml-indent-step:1
sgml-indent-data:t
indent-tabs-mode:nil
sgml-parent-document:nil
sgml-default-dtd-file:"../../manual.ced"
sgml-exposed-tags:nil
sgml-local-catalogs:nil
sgml-local-ecat-files:nil
End:
vim600: syn=xml fen fdm=syntax fdl=2 si
vim: et tw=78 syn=sgml
vi: ts=1 sw=1
-->