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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision$ -->
<!-- splitted from ./index.xml, last change in rev 1.66 -->
<chapter xml:id="security.hiding" xmlns="http://docbook.org/ns/docbook">
<title>Hiding PHP</title>
<para>
In general, security by obscurity is one of the weakest forms of security.
But in some cases, every little bit of extra security is desirable.
</para>
<para>
A few simple techniques can help to hide <acronym>PHP</acronym>, possibly slowing
down an attacker who is attempting to discover weaknesses in your
system. By setting expose_php to <literal>off</literal> in your
&php.ini; file, you reduce the amount of information available to them.
</para>
<para>
Another tactic is to configure web servers such as apache to
parse different filetypes through <acronym>PHP</acronym>, either with an &htaccess;
directive, or in the apache configuration file itself. You can
then use misleading file extensions:
<example>
<title>Hiding PHP as another language</title>
<programlisting role="apache-conf">
<![CDATA[
# Make PHP code look like other code types
AddType application/x-httpd-php .asp .py .pl
]]>
</programlisting>
</example>
Or obscure it completely:
<example>
<title>Using unknown types for PHP extensions</title>
<programlisting role="apache-conf">
<![CDATA[
# Make PHP code look like unknown types
AddType application/x-httpd-php .bop .foo .133t
]]>
</programlisting>
</example>
Or hide it as <acronym>HTML</acronym> code, which has a slight performance hit because
all <acronym>HTML</acronym> will be parsed through the <acronym>PHP</acronym> engine:
<example>
<title>Using <acronym>HTML</acronym> types for PHP extensions</title>
<programlisting role="apache-conf">
<![CDATA[
# Make all PHP code look like HTML
AddType application/x-httpd-php .htm .html
]]>
</programlisting>
</example>
For this to work effectively, you must rename your <acronym>PHP</acronym> files with
the above extensions. While it is a form of security through
obscurity, it's a minor preventative measure with few drawbacks.
</para>
</chapter>
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