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<?xml version="1.0" encoding="utf-8"?>
<!-- $Revision: 332710 $ -->
<book xml:id="book.session" xmlns="http://docbook.org/ns/docbook" xmlns:xlink="http://www.w3.org/1999/xlink">
<?phpdoc extension-membership="core" ?>
<title>Session Handling</title>
<titleabbrev>Sessions</titleabbrev>
<!-- {{{ preface -->
<preface xml:id="intro.session">
&reftitle.intro;
<para>
Session support in PHP consists of a way to preserve certain data
across subsequent accesses. This enables you to build more
customized applications and increase the appeal of your web site.
</para>
<para>
A visitor accessing your web site is assigned a unique id, the
so-called session id. This is either stored in a cookie on the
user side or is propagated in the URL.
</para>
<para>
The session support allows you to store data between requests in the
<varname>$_SESSION</varname> superglobal array. When a visitor accesses
your site, PHP will check automatically (if <link linkend="ini.session.auto-start">session.auto_start</link>
is set to 1) or on your request (explicitly through
<function>session_start</function>) whether a specific session
id has been sent with the request. If this is the case, the prior
saved environment is recreated.
</para>
<caution>
<para>
If you turn on <link linkend="ini.session.auto-start">
session.auto_start</link> then the only way to put objects
into your sessions is to load its class definition using
<link linkend="ini.auto-prepend-file">auto_prepend_file</link>
in which you load the class definition else you will have to
<function>serialize</function> your object
and <function>unserialize</function> it
afterwards.
</para>
</caution>
<para>
<varname>$_SESSION</varname> (and all registered variables) are serialized
internally by PHP using the serialization handler specified by the
<link linkend="ini.session.serialize-handler">session.serialize_handler</link> ini setting,
after the request finishes. Registered variables which are undefined are
marked as being not defined. On subsequent accesses, these are not defined
by the session module unless the user defines them later.
</para>
<warning>
<para>
Because session data is serialized, <type>resource</type> variables cannot
be stored in the session.
</para>
<para>
Serialize handlers (<literal>php</literal>
and <literal>php_binary</literal>) inherit register_globals
limitations. Therefore, numeric index or string index contains
special characters (<literal>|</literal>
and <literal>!</literal>) cannot be used. Using these will end up
with errors at script shutdown. <literal>php_serialize</literal>
does not have such limitations. <literal>php_serialize</literal>
is available from PHP 5.5.4.
</para>
</warning>
<note>
<para>
Please note when working with sessions that a record of a session
is not created until a variable has been registered using the
<function>session_register</function> function or by adding a new
key to the <varname>$_SESSION</varname> superglobal array. This
holds true regardless of if a session has been started using the
<function>session_start</function> function.
</para>
</note>
<note>
<para>
PHP 5.2.2 introduced an undocumented feature to store session files
in "/tmp" even if <link linkend="ini.open-basedir">open_basedir</link>
was enabled and "/tmp" is not explicitly added to the allowed paths
list. This feature has been removed from PHP as of PHP 5.3.0.
</para>
</note>
</preface>
<!-- }}} -->
&reference.session.setup;
&reference.session.constants;
&reference.session.examples;
&reference.session.upload-progress;
&reference.session.security;
&reference.session.reference;
&reference.session.sessionhandler;
&reference.session.sessionhandlerinterface;
</book>
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vi: ts=1 sw=1
-->
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