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><DIV
CLASS="reference"
><A
NAME="ref.session"
></A
><DIV
CLASS="TITLEPAGE"
><H1
CLASS="title"
>XCIII. Session handling functions</H1
><DIV
CLASS="PARTINTRO"
><A
NAME="AEN83869"
></A
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.intro"
></A
>Introduction</H1
><P
> 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.
</P
><P
> If you are familiar with the session management of PHPLIB, you
will notice that some concepts are similar to PHP's session
support.
</P
><P
> A visitor accessing your web site is assigned an unique id, the
so-called session id. This is either stored in a cookie on the
user side or is propagated in the URL.
</P
><P
> The session support allows you to register arbitrary numbers of
variables to be preserved across requests. When a visitor accesses
your site, PHP will check automatically (if session.auto_start is
set to 1) or on your request (explicitly through
<A
HREF="function.session-start.html"
><B
CLASS="function"
>session_start()</B
></A
> or implicitly through
<A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
>) whether a specific session
id has been sent with the request. If this is the case, the prior
saved environment is recreated.
</P
><P
> All registered variables are serialized 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.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Session handling was added in PHP 4.0.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Please note when working with sessions that a record of a session
is not created until a variable has been registered using the
<A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
> function or by adding a new
key to the <TT
CLASS="varname"
>$_SESSION</TT
> superglobal array. This
holds true regardless of if a session has been started using the
<A
HREF="function.session-start.html"
><B
CLASS="function"
>session_start()</B
></A
> function.
</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.security"
></A
>Sessions and security</H1
><P
> External links: <A
HREF="http://www.acros.si/papers/session_fixation.pdf"
TARGET="_top"
>Session fixation</A
>
</P
><P
> The session module cannot guarantee that the information you store
in a session is only viewed by the user who created the session. You need
to take additional measures to actively protect the integrity of the
session, depending on the value associated with it.
</P
><P
> Assess the importance of the data carried by your sessions and deploy
addditional protections -- this usually comes at a price, reduced
convenience for the user. For example, if you want to protect users from
simple social engineering tactics, you need to enable
session.use_only_cookies. In that case, cookies must be enabled
unconditionally on the user side, or sessions will not work.
</P
><P
> There are several ways to leak an existing session id to third parties.
A leaked session id enables the third party to access all resources which
are associated with a specific id. First, URLs carrying session ids. If
you link to an external site, the URL including the session id might be
stored in the external site's referrer logs. Second, a more active
attacker might listen to your network traffic. If it is not encrypted,
session ids will flow in plain text over the network. The solution here
is to implement SSL on your server and make it mandatory for users.
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.requirements"
></A
>Requirements</H1
><P
>No external libraries are needed to build this extension.</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Optionally you can use shared memory allocation (mm), developed by
Ralf S. Engelschall, for session storage. You have to download
<A
HREF="http://www.ossp.org/pkg/lib/mm/"
TARGET="_top"
>mm</A
> and install it. This option is not
available for Windows platforms. Note that the session storage module
for mm does not guarantee that concurrent accesses to the same session
are properly locked. It might be more appropiate to use a shared memory
based filesystem (such as tmpfs on Solaris/Linux, or /dev/md on BSD) to
store sessions in files, because they are properly locked.
</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.installation"
></A
>Installation</H1
><P
> Session support is enabled in PHP by default. If you would
not like to build your PHP with session support, you should
specify the <TT
CLASS="option"
>--disable-session</TT
>
option to configure. To use shared memory allocation (mm) for session
storage configure PHP <TT
CLASS="option"
>--with-mm[=DIR] </TT
>.
</P
><P
> The windows version of <TT
CLASS="literal"
>PHP</TT
>
has built in support for this extension. You do not need to load any additional
extension in order to use these functions.</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.configuration"
></A
>Runtime Configuration</H1
><P
> The behaviour of these functions is affected by settings in <TT
CLASS="filename"
>php.ini</TT
>.
</P
><P
> <DIV
CLASS="table"
><A
NAME="AEN83911"
></A
><P
><B
>Table 1. Session configuration options</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><THEAD
><TR
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Name</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Default</TH
><TH
ALIGN="LEFT"
VALIGN="MIDDLE"
>Changeable</TH
></TR
></THEAD
><TBODY
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.save_path</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"/tmp"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.name</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"PHPSESSID"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.save_handler</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"files"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.auto_start</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.gc_probability</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"1"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.gc_maxlifetime</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"1440"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.serialize_handler</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"php"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cookie_lifetime</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cookie_path</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"/"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cookie_domain</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cookie_secure</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.use_cookies</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"1"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.use_only_cookies</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.referer_check</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.entropy_file</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>""</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.entropy_length</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cache_limiter</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"nocache"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.cache_expire</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"180"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>session.use_trans_sid</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"0"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_SYSTEM|PHP_INI_PERDIR</TD
></TR
><TR
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>url_rewriter.tags</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>"a=href,area=href,frame=src,input=src,form=fakeentry"</TD
><TD
ALIGN="LEFT"
VALIGN="MIDDLE"
>PHP_INI_ALL</TD
></TR
></TBODY
></TABLE
></DIV
>
For further details and definition of the PHP_INI_* constants see
<A
HREF="function.ini-set.html"
><B
CLASS="function"
>ini_set()</B
></A
>.
</P
><P
> The session management system supports a number of configuration
options which you can place in your <TT
CLASS="filename"
>php.ini</TT
> file. We will give a
short overview.
<P
></P
><DIV
CLASS="variablelist"
><DL
><DT
><A
NAME="ini.session.save-handler"
></A
><TT
CLASS="parameter"
><I
>session.save_handler</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.save_handler</TT
> defines the name of the
handler which is used for storing and retrieving data
associated with a session. Defaults to
<TT
CLASS="literal"
>files</TT
>. See also
<A
HREF="function.session-set-save-handler.html"
><B
CLASS="function"
>session_set_save_handler()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.save-path"
></A
><TT
CLASS="parameter"
><I
>session.save_path</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.save_path</TT
> defines the argument which
is passed to the save handler. If you choose the default files
handler, this is the path where the files are created.
Defaults to <TT
CLASS="literal"
>/tmp</TT
>. If
<TT
CLASS="literal"
>session.save_path</TT
>'s path depth is more than
2, garbage collection will not be performed. See also
<A
HREF="function.session-save-path.html"
><B
CLASS="function"
>session_save_path()</B
></A
>.
</P
><DIV
CLASS="warning"
><P
></P
><TABLE
CLASS="warning"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Warning</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
> If you leave this set to a world-readable directory, such as
<TT
CLASS="filename"
>/tmp</TT
> (the default), other users on the
server may be able to hijack sessions by getting the list of
files in that directory.
</P
></TD
></TR
></TABLE
></DIV
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Windows users have to change this variable in order to use PHP's
session functions. Make sure to specify a valid path, e.g.:
<TT
CLASS="filename"
>c:/temp</TT
>.
</P
></BLOCKQUOTE
></DIV
></DD
><DT
><A
NAME="ini.session.name"
></A
><TT
CLASS="parameter"
><I
>session.name</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.name</TT
> specifies the name of the
session which is used as cookie name. It should only contain
alphanumeric characters. Defaults to <TT
CLASS="literal"
>PHPSESSID</TT
>.
See also <A
HREF="function.session-name.html"
><B
CLASS="function"
>session_name()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.auto-start"
></A
><TT
CLASS="parameter"
><I
>session.auto_start</I
></TT
>
<A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.auto_start</TT
> specifies whether the
session module starts a session automatically on request
startup. Defaults to <TT
CLASS="literal"
>0</TT
> (disabled).
</P
></DD
><DT
><A
NAME="ini.session.serialize-handler"
></A
><TT
CLASS="parameter"
><I
>session.serialize_handler</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.serialize_handler</TT
> defines the name
of the handler which is used to serialize/deserialize
data. Currently, a PHP internal format (name
<TT
CLASS="literal"
>php</TT
>) and WDDX is supported (name
<TT
CLASS="literal"
>wddx</TT
>). WDDX is only available, if PHP is
compiled with <A
HREF="ref.wddx.html"
>WDDX
support</A
>. Defaults to <TT
CLASS="literal"
>php</TT
>.
</P
></DD
><DT
><A
NAME="ini.session.gc-probability"
></A
><TT
CLASS="parameter"
><I
>session.gc_probability</I
></TT
>
<A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.gc_probability</TT
> specifies the
probability that the gc (garbage collection) routine is started
on each request in percent. Defaults to <TT
CLASS="literal"
>1</TT
>.
</P
></DD
><DT
><A
NAME="ini.session.gc-maxlifetime"
></A
><TT
CLASS="parameter"
><I
>session.gc_maxlifetime</I
></TT
>
<A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.gc_maxlifetime</TT
> specifies the number
of seconds after which data will be seen as 'garbage' and
cleaned up.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>If you are using the default file-based session handler, your
filesystem must keep track of access times (atime). Windows FAT does
not so you will have to come up with another way to handle garbage
collecting your session if you are stuck with a FAT filesystem or any
other fs where atime tracking is not available.
</P
></BLOCKQUOTE
></DIV
></DD
><DT
><A
NAME="ini.session.referer-check"
></A
><TT
CLASS="parameter"
><I
>session.referer_check</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.referer_check</TT
> contains the
substring you want to check each HTTP Referer for. If the
Referer was sent by the client and the substring was not
found, the embedded session id will be marked as invalid.
Defaults to the empty string.
</P
></DD
><DT
><A
NAME="ini.session.entropy-file"
></A
><TT
CLASS="parameter"
><I
>session.entropy_file</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.entropy_file</TT
> gives a path to an
external resource (file) which will be used as an additional
entropy source in the session id creation process. Examples are
<TT
CLASS="literal"
>/dev/random</TT
> or <TT
CLASS="literal"
>/dev/urandom</TT
>
which are available on many Unix systems.
</P
></DD
><DT
><A
NAME="ini.session.entropy-length"
></A
><TT
CLASS="parameter"
><I
>session.entropy_length</I
></TT
>
<A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.entropy_length</TT
> specifies the number
of bytes which will be read from the file specified
above. Defaults to <TT
CLASS="literal"
>0</TT
> (disabled).
</P
></DD
><DT
><A
NAME="ini.session.use-cookies"
></A
><TT
CLASS="parameter"
><I
>session.use_cookies</I
></TT
>
<A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.use_cookies</TT
> specifies whether the
module will use cookies to store the session id on the client
side. Defaults to <TT
CLASS="literal"
>1</TT
> (enabled).
</P
></DD
><DT
><A
NAME="ini.session.use-only_cookies"
></A
><TT
CLASS="parameter"
><I
>session.use_only_cookies</I
></TT
>
<A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.use_only_cookies</TT
> specifies whether
the module will <SPAN
CLASS="strong"
><B
CLASS="emphasis"
>only</B
></SPAN
> use
cookies to store the session id on the client side. Defaults
to <TT
CLASS="literal"
>0</TT
> (disabled, for backward compatibility).
Enabling this setting prevents attacks involved passing session
ids in URLs. This setting was added in <TT
CLASS="literal"
>PHP</TT
>
4.3.0.
</P
></DD
><DT
><A
NAME="ini.session.cookie-lifetime"
></A
><TT
CLASS="parameter"
><I
>session.cookie_lifetime</I
></TT
>
<A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cookie_lifetime</TT
> specifies the lifetime of
the cookie in seconds which is sent to the browser. The value 0
means "until the browser is closed." Defaults to
<TT
CLASS="literal"
>0</TT
>.See also
<A
HREF="function.session-get-cookie-params.html"
><B
CLASS="function"
>session_get_cookie_params()</B
></A
> and
<A
HREF="function.session-set-cookie-params.html"
><B
CLASS="function"
>session_set_cookie_params()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.cookie-path"
></A
><TT
CLASS="parameter"
><I
>session.cookie_path</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cookie_path</TT
> specifies path to set
in session_cookie. Defaults to <TT
CLASS="literal"
>/</TT
>.See also
<A
HREF="function.session-get-cookie-params.html"
><B
CLASS="function"
>session_get_cookie_params()</B
></A
> and
<A
HREF="function.session-set-cookie-params.html"
><B
CLASS="function"
>session_set_cookie_params()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.cookie-domain"
></A
><TT
CLASS="parameter"
><I
>session.cookie_domain</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cookie_domain</TT
> specifies the domain to
set in session_cookie. Default is none at all. See also
<A
HREF="function.session-get-cookie-params.html"
><B
CLASS="function"
>session_get_cookie_params()</B
></A
> and
<A
HREF="function.session-set-cookie-params.html"
><B
CLASS="function"
>session_set_cookie_params()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.cookie-secure"
></A
><TT
CLASS="parameter"
><I
>session.cookie_secure</I
></TT
>
<A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cookie_secure</TT
> specifies whether
cookies should only be sent over secure connections. Defaults to
<TT
CLASS="literal"
>off</TT
>.
This setting was added in <TT
CLASS="literal"
>PHP</TT
>
4.0.4. See also
<A
HREF="function.session-get-cookie-params.html"
><B
CLASS="function"
>session_get_cookie_params()</B
></A
> and
<A
HREF="function.session-set-cookie-params.html"
><B
CLASS="function"
>session_set_cookie_params()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.cache-limiter"
></A
><TT
CLASS="parameter"
><I
>session.cache_limiter</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cache_limiter</TT
> specifies cache
control method to use for session pages
(none/nocache/private/private_no_expire/public). Defaults to
<TT
CLASS="literal"
>nocache</TT
>. See also
<A
HREF="function.session-cache-limiter.html"
><B
CLASS="function"
>session_cache_limiter()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.cache-expire"
></A
><TT
CLASS="parameter"
><I
>session.cache_expire</I
></TT
>
<A
HREF="language.types.integer.html"
><B
CLASS="type"
>integer</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.cache_expire</TT
> specifies time-to-live
for cached session pages in minutes, this has no effect for
nocache limiter. Defaults to <TT
CLASS="literal"
>180</TT
>. See also
<A
HREF="function.session-cache-expire.html"
><B
CLASS="function"
>session_cache_expire()</B
></A
>.
</P
></DD
><DT
><A
NAME="ini.session.use-trans_sid"
></A
><TT
CLASS="parameter"
><I
>session.use_trans_sid</I
></TT
>
<A
HREF="language.types.boolean.html"
><B
CLASS="type"
>boolean</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>session.use_trans_sid</TT
> whether transparent
sid support is enabled or not. Defaults to
<TT
CLASS="literal"
>0</TT
> (disabled).
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
For PHP 4.1.2 or less, it is enabled by compiling with
<A
HREF="install.configure.html#install.configure.enable-trans-sid"
> <TT
CLASS="literal"
>--enable-trans-sid</TT
></A
>.
From PHP 4.2.0, trans-sid feature is always compiled.
</P
><P
> URL based session management has additional security risks
compared to cookie based session management. Users may send
an URL that contains an active session ID to their friends by
email or users may save an URL that contains a session ID to
their bookmarks and access your site with the same session ID
always, for example.
</P
></BLOCKQUOTE
></DIV
></DD
><DT
><A
NAME="ini.url-rewriter.tags"
></A
><TT
CLASS="parameter"
><I
>url_rewriter.tags</I
></TT
>
<A
HREF="language.types.string.html"
><B
CLASS="type"
>string</B
></A
></DT
><DD
><P
> <TT
CLASS="literal"
>url_rewriter.tags</TT
> specifies which html tags
are rewritten to include session id if transparent sid support
is enabled. Defaults to
<TT
CLASS="literal"
>a=href,area=href,frame=src,input=src,form=fakeentry</TT
>
</P
></DD
></DL
></DIV
>
</P
><P
> The <A
HREF="configuration.directives.html#ini.track-vars"
><TT
CLASS="literal"
>track_vars</TT
></A
> and
<A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
configuration settings influence how the session variables get
stored and restored.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
As of PHP 4.0.3, <A
HREF="configuration.directives.html#ini.track-vars"
><TT
CLASS="literal"
>track_vars</TT
></A
> is
always turned on.
</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.resources"
></A
>Resource Types</H1
><P
>This extension has no resource types defined.</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.constants"
></A
>Predefined Constants</H1
><P
> The constants below are defined by this extension, and
will only be available when the extension has either
been compiled into PHP or dynamically loaded at runtime.
</P
><P
></P
><DIV
CLASS="variablelist"
><DL
><DT
><TT
CLASS="constant"
><B
>SID</B
></TT
>
(<A
HREF="language.types.string.html"
>string</A
>)</DT
><DD
><P
> Constant containing the session name and session ID in
the form of <TT
CLASS="literal"
>"name=ID"</TT
>.
</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.examples"
></A
>Examples</H1
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
As of PHP 4.1.0, <TT
CLASS="varname"
>$_SESSION</TT
> is available as a
global variable just like <TT
CLASS="varname"
>$_POST</TT
>,
<TT
CLASS="varname"
>$_GET</TT
>, <TT
CLASS="varname"
>$_REQUEST</TT
> and so on.
Unlike <TT
CLASS="varname"
>$HTTP_SESSION_VARS</TT
>,
<TT
CLASS="varname"
>$_SESSION</TT
> is always global. Therefore, you do not
need to use the <A
HREF="language.variables.scope.html"
><B
CLASS="command"
>global</B
></A
>
keyword for <TT
CLASS="varname"
>$_SESSION</TT
>. Please note that this
documentation has been changed to use
<TT
CLASS="varname"
>$_SESSION</TT
> everywhere. You can substitute
<TT
CLASS="varname"
>$HTTP_SESSION_VARS</TT
> for
<TT
CLASS="varname"
>$_SESSION</TT
>, if you prefer the former. Also note
that you must start your session using <A
HREF="function.session-start.html"
><B
CLASS="function"
>session_start()</B
></A
>
before use of <TT
CLASS="varname"
>$_SESSION</TT
> becomes available.
</P
><P
> The keys in the <TT
CLASS="varname"
>$_SESSION</TT
> associative
array are subject to the
same limitations as regular variable names in PHP, i.e. they cannot
start with a number and must start with a letter or underscore.
For more details see the section on
<A
HREF="language.variables.html"
>variables</A
> in this manual.
</P
></BLOCKQUOTE
></DIV
><P
> If <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
is disabled, only members of the global associative array
<TT
CLASS="varname"
>$_SESSION</TT
> can be registered as session
variables. The restored session variables will only be available
in the array <TT
CLASS="varname"
>$_SESSION</TT
>.
</P
><P
> Use of <TT
CLASS="varname"
>$_SESSION</TT
> (or
<TT
CLASS="varname"
>$HTTP_SESSION_VARS</TT
> with PHP 4.0.6 or less) is
recommended for improved security and code readablity. With
<TT
CLASS="varname"
>$_SESSION</TT
>, there is no need to use the
<A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
>,
<A
HREF="function.session-unregister.html"
><B
CLASS="function"
>session_unregister()</B
></A
>,
<A
HREF="function.session-is-registered.html"
><B
CLASS="function"
>session_is_registered()</B
></A
> functions. Session variables
are accessible like any other variables.
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN84251"
></A
><P
><B
>Example 1.
Registering a variable with $_SESSION.
</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
session_start();
// Use $HTTP_SESSION_VARS with PHP 4.0.6 or less
if (!isset($_SESSION['count'])) {
$_SESSION['count'] = 0;
} else {
$_SESSION['count']++;
}
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN84254"
></A
><P
><B
>Example 2.
Unregistering a variable with $_SESSION and register_globals disabled.
</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
session_start();
// Use $HTTP_SESSION_VARS with PHP 4.0.6 or less
unset($_SESSION['count']);
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN84257"
></A
><P
><B
>Example 3.
Unregistering a variable with register_globals enabled, after
registering it using $_SESSION.
</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
session_start();
// With PHP 4.3 and later, you can also simply use the prior example.
session_unregister('count');
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
><P
> If <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
is enabled, then each global variable can be registered as session
variable. Upon a restart of a session, these variables will be restored
to corresponding global variables. Since PHP must know which global
variables are registered as session variables, users need to register
variables with <A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
> function.
You can avoid this by simply setting entries in
<TT
CLASS="varname"
>$_SESSION</TT
>.
<DIV
CLASS="caution"
><P
></P
><TABLE
CLASS="caution"
BORDER="1"
WIDTH="100%"
><TR
><TD
ALIGN="CENTER"
><B
>Caution</B
></TD
></TR
><TR
><TD
ALIGN="LEFT"
><P
> If you are using
<TT
CLASS="varname"
>$_SESSION</TT
>
and disable <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>,
do not use <A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
>,
<A
HREF="function.session-is-registered.html"
><B
CLASS="function"
>session_is_registered()</B
></A
> and
<A
HREF="function.session-unregister.html"
><B
CLASS="function"
>session_unregister()</B
></A
>, if your scripts shall work
in PHP 4.2 and earlier. You can use these functions in 4.3 and later.
</P
><P
> If you enable <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>,
<A
HREF="function.session-unregister.html"
><B
CLASS="function"
>session_unregister()</B
></A
> should be used since
session variables are registered as global variables when
session data is deserialized. Disabling <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
is recommended for both security and performance reasons.
</P
></TD
></TR
></TABLE
></DIV
>
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN84279"
></A
><P
><B
>Example 4.
Registering a variable with <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
enabled
</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
if (!session_is_registered('count')) {
session_register("count");
$count = 0;
}
else {
$count++;
}
?></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
><P
> If <A
HREF="configuration.directives.html#ini.register-globals"
><TT
CLASS="literal"
>register_globals</TT
></A
>
is enabled, then the global variables and the
<TT
CLASS="varname"
>$_SESSION</TT
> entries will automatically reference the
same values which were registered in the prior session instance.
</P
><P
> There is a defect in PHP 4.2.3 and earlier. If you register a new
session variable by using <A
HREF="function.session-register.html"
><B
CLASS="function"
>session_register()</B
></A
>, the
entry in the global scope and the <TT
CLASS="varname"
>$_SESSION</TT
> entry will
not reference the same value until the next
<A
HREF="function.session-start.html"
><B
CLASS="function"
>session_start()</B
></A
>. I.e. a modification to the newly
registered global variable will not be reflected by the
<TT
CLASS="varname"
>$_SESSION</TT
> entry. This has been corrected in PHP 4.3.
</P
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.idpassing"
></A
>Passing the Session ID</H1
><P
> There are two methods to propagate a session id:
<P
></P
><UL
><LI
><P
> Cookies
</P
></LI
><LI
><P
> URL parameter
</P
></LI
></UL
>
</P
><P
> The session module supports both methods. Cookies are optimal, but
because they are not always available, we also provide an alternative
way. The second method embeds the session id directly into URLs.
</P
><P
> PHP is capable of transforming links transparently. Unless you are using
PHP 4.2 or later, you need to enable it manually when building PHP.
Under UNIX, pass <A
HREF="install.configure.html#install.configure.enable-trans-sid"
> <TT
CLASS="literal"
>--enable-trans-sid</TT
></A
> to configure. If this build
option and the run-time option session.use_trans_sid are enabled,
relative URIs will be changed to contain the session id automatically.
<DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
The <A
HREF="configuration.directives.html#ini.arg-separator.output"
>arg_separator.output</A
>
<TT
CLASS="filename"
>php.ini</TT
> directive allows to customize the argument seperator. For full
XHTML conformance, specify &amp; there.
</P
></BLOCKQUOTE
></DIV
>
</P
><P
> Alternatively, you can use the constant <TT
CLASS="literal"
>SID</TT
> which is
always defined. If the client did not send an appropriate session
cookie, it has the form <TT
CLASS="literal"
>session_name=session_id</TT
>.
Otherwise, it expands to an empty string. Thus, you can embed it
unconditionally into URLs.
</P
><P
> The following example demonstrates how to register a variable, and
how to link correctly to another page using SID.
<TABLE
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
CLASS="EXAMPLE"
><TR
><TD
><DIV
CLASS="example"
><A
NAME="AEN84313"
></A
><P
><B
>Example 5. Counting the number of hits of a single user</B
></P
><TABLE
BORDER="0"
BGCOLOR="#E0E0E0"
CELLPADDING="5"
><TR
><TD
><PRE
CLASS="php"
><?php
if (!session_is_registered('count')) {
session_register('count');
$count = 1;
}
else {
$count++;
}
?>
Hello visitor, you have seen this page <?php echo $count; ?> times.<p>
To continue, <A HREF="nextpage.php?<?php echo SID?>">click here</A></PRE
></TD
></TR
></TABLE
></DIV
></TD
></TR
></TABLE
>
</P
><P
> The <TT
CLASS="literal"
><?php echo SID?></TT
>
(<TT
CLASS="literal"
><?=SID?></TT
> can be used if
<A
HREF="configuration.directives.html#ini.short-open-tag"
>short_open_tag</A
> is enabled) is
necessary to preserve the session id in the case that the user has
disabled cookies.
The <TT
CLASS="literal"
><?=SID?></TT
> is not necessary, if
<A
HREF="install.configure.html#install.configure.enable-trans-sid"
> <TT
CLASS="literal"
>--enable-trans-sid</TT
></A
> was used to compile PHP.
</P
><DIV
CLASS="note"
><BLOCKQUOTE
CLASS="note"
><P
><B
>Note: </B
>
Non-relative URLs are assumed to point to external sites and
hence don't append the SID, as it would be a security risk to
leak the SID to a different server.
</P
></BLOCKQUOTE
></DIV
></DIV
><DIV
CLASS="section"
><H1
CLASS="section"
><A
NAME="session.customhandler"
></A
>Custom Session Handlers</H1
><P
> To implement database storage, or any other storage method, you
will need to use <A
HREF="function.session-set-save-handler.html"
><B
CLASS="function"
>session_set_save_handler()</B
></A
> to
create a set of user-level storage functions.
</P
></DIV
></DIV
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
><A
HREF="function.session-cache-expire.html"
>session_cache_expire</A
> -- Return current cache expire</DT
><DT
><A
HREF="function.session-cache-limiter.html"
>session_cache_limiter</A
> -- Get and/or set the current cache limiter</DT
><DT
><A
HREF="function.session-decode.html"
>session_decode</A
> -- Decodes session data from a string</DT
><DT
><A
HREF="function.session-destroy.html"
>session_destroy</A
> -- Destroys all data registered to a session</DT
><DT
><A
HREF="function.session-encode.html"
>session_encode</A
> --
Encodes the current session data as a string
</DT
><DT
><A
HREF="function.session-get-cookie-params.html"
>session_get_cookie_params</A
> --
Get the session cookie parameters
</DT
><DT
><A
HREF="function.session-id.html"
>session_id</A
> -- Get and/or set the current session id</DT
><DT
><A
HREF="function.session-is-registered.html"
>session_is_registered</A
> --
Find out whether a global variable is registered in a session
</DT
><DT
><A
HREF="function.session-module-name.html"
>session_module_name</A
> -- Get and/or set the current session module</DT
><DT
><A
HREF="function.session-name.html"
>session_name</A
> -- Get and/or set the current session name</DT
><DT
><A
HREF="function.session-readonly.html"
>session_readonly</A
> -- Begin session - reinitializes frozen variables, but no writeback on request end</DT
><DT
><A
HREF="function.session-register.html"
>session_register</A
> --
Register one or more global variables with the current session
</DT
><DT
><A
HREF="function.session-save-path.html"
>session_save_path</A
> -- Get and/or set the current session save path</DT
><DT
><A
HREF="function.session-set-cookie-params.html"
>session_set_cookie_params</A
> --
Set the session cookie parameters
</DT
><DT
><A
HREF="function.session-set-save-handler.html"
>session_set_save_handler</A
> --
Sets user-level session storage functions
</DT
><DT
><A
HREF="function.session-start.html"
>session_start</A
> -- Initialize session data</DT
><DT
><A
HREF="function.session-unregister.html"
>session_unregister</A
> --
Unregister a global variable from the current session
</DT
><DT
><A
HREF="function.session-unset.html"
>session_unset</A
> --
Free all session variables
</DT
><DT
><A
HREF="function.session-write-close.html"
>session_write_close</A
> -- Write session data and end session</DT
></DL
></DIV
></DIV
></DIV
><DIV
CLASS="NAVFOOTER"
><HR
ALIGN="LEFT"
WIDTH="100%"><TABLE
SUMMARY="Footer navigation table"
WIDTH="100%"
BORDER="0"
CELLPADDING="0"
CELLSPACING="0"
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
><A
HREF="function.sesam-settransaction.html"
ACCESSKEY="P"
>Prev</A
></TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="index.html"
ACCESSKEY="H"
>Home</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
><A
HREF="function.session-cache-expire.html"
ACCESSKEY="N"
>Next</A
></TD
></TR
><TR
><TD
WIDTH="33%"
ALIGN="left"
VALIGN="top"
>sesam_settransaction</TD
><TD
WIDTH="34%"
ALIGN="center"
VALIGN="top"
><A
HREF="funcref.html"
ACCESSKEY="U"
>Up</A
></TD
><TD
WIDTH="33%"
ALIGN="right"
VALIGN="top"
>session_cache_expire</TD
></TR
></TABLE
></DIV
></BODY
></HTML
>
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