Runtime Configuration

The behaviour of these functions is affected by settings in php.ini.

Session configuration options

Name	Default	Changeable	Changelog
session.save_path	""	PHP_INI_ALL
session.name	"PHPSESSID"	PHP_INI_ALL
session.save_handler	"files"	PHP_INI_ALL
session.auto_start	"0"	PHP_INI_ALL
session.gc_probability	"1"	PHP_INI_ALL
session.gc_divisor	"100"	PHP_INI_ALL	Available since PHP 4.3.2.
session.gc_maxlifetime	"1440"	PHP_INI_ALL
session.serialize_handler	"php"	PHP_INI_ALL
session.cookie_lifetime	"0"	PHP_INI_ALL
session.cookie_path	"/"	PHP_INI_ALL
session.cookie_domain	""	PHP_INI_ALL
session.cookie_secure	""	PHP_INI_ALL	Available since PHP 4.0.4.
session.cookie_httponly	""	PHP_INI_ALL	Available since PHP 5.2.0.
session.use_cookies	"1"	PHP_INI_ALL
session.use_only_cookies	"1"	PHP_INI_ALL	Available since PHP 4.3.0.
session.referer_check	""	PHP_INI_ALL
session.entropy_file	""	PHP_INI_ALL
session.entropy_length	"0"	PHP_INI_ALL
session.cache_limiter	"nocache"	PHP_INI_ALL
session.cache_expire	"180"	PHP_INI_ALL
session.use_trans_sid	"0"	PHP_INI_ALL	PHP_INI_ALL in PHP <= 4.2.3. PHP_INI_PERDIR in PHP < 5. Available since PHP 4.0.3.
session.bug_compat_42	"1"	PHP_INI_ALL	Available since PHP 4.3.0. Removed in PHP 6.0.0.
session.bug_compat_warn	"1"	PHP_INI_ALL	Available since PHP 4.3.0. Removed in PHP 6.0.0.
session.hash_function	"0"	PHP_INI_ALL	Available since PHP 5.0.0.
session.hash_bits_per_character	"4"	PHP_INI_ALL	Available since PHP 5.0.0.
url_rewriter.tags	"a=href,area=href,frame=src,form=,fieldset="	PHP_INI_ALL	Available since PHP 4.0.4.

For further details and definitions of the PHP_INI_* constants, see the php.ini directives.

The session management system supports a number of configuration options which you can place in your php.ini file. We will give a short overview.

session.save_handler string

session.save_handler defines the name of the handler which is used for storing and retrieving data associated with a session. Defaults to files. Note that individual extensions may register their own save_handlers; registered handlers can be obtained on a per-installation basis by referring to phpinfo(). See also session_set_save_handler().

session.save_path string

session.save_path 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. See also session_save_path().

There is an optional N argument to this directive that determines the number of directory levels your session files will be spread around in. For example, setting to '5;/tmp' may end up creating a session file and location like /tmp/4/b/1/e/3/sess_4b1e384ad74619bd212e236e52a5a174If . In order to use N you must create all of these directories before use. A small shell script exists in ext/session to do this, it's called mod_files.sh. Also note that if N is used and greater than 0 then automatic garbage collection will not be performed, see a copy of php.ini for further information. Also, if you use N, be sure to surround session.save_path in "quotes" because the separator (;) is also used for comments in php.ini.

Warning

If you leave this set to a world-readable directory, such as /tmp (the default), other users on the server may be able to hijack sessions by getting the list of files in that directory.

Note: Prior to PHP 4.3.6, Windows users had to change this variable in order to use PHP's session functions. A valid path must be specified, e.g.: c:/temp.

session.name string

session.name specifies the name of the session which is used as cookie name. It should only contain alphanumeric characters. Defaults to PHPSESSID. See also session_name().

session.auto_start boolean

session.auto_start specifies whether the session module starts a session automatically on request startup. Defaults to 0 (disabled).

session.serialize_handler string

session.serialize_handler defines the name of the handler which is used to serialize/deserialize data. Currently, a PHP internal format (name php or php_binary) and WDDX are supported (name wddx). WDDX is only available, if PHP is compiled with WDDX support. Defaults to php.

session.gc_probability integer

session.gc_probability in conjunction with session.gc_divisor is used to manage probability that the gc (garbage collection) routine is started. Defaults to 1. See session.gc_divisor for details.

session.gc_divisor integer

session.gc_divisor coupled with session.gc_probability defines the probability that the gc (garbage collection) process is started on every session initialization. The probability is calculated by using gc_probability/gc_divisor, e.g. 1/100 means there is a 1% chance that the GC process starts on each request. session.gc_divisor defaults to 100.

session.gc_maxlifetime integer

session.gc_maxlifetime specifies the number of seconds after which data will be seen as 'garbage' and cleaned up. Garbage collection occurs during session start.

Note: If different scripts have different values of session.gc_maxlifetime but share the same place for storing the session data then the script with the minimum value will be cleaning the data. In this case, use this directive together with session.save_path.

Note: 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 filesystem where atime tracking is not available. Since PHP 4.2.3 it has used mtime (modified date) instead of atime. So, you won't have problems with filesystems where atime tracking is not available.

session.referer_check string

session.referer_check 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.

session.entropy_file string

session.entropy_file 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 /dev/random or /dev/urandom which are available on many Unix systems.

session.entropy_length integer

session.entropy_length specifies the number of bytes which will be read from the file specified above. Defaults to 0 (disabled).

session.use_cookies boolean

session.use_cookies specifies whether the module will use cookies to store the session id on the client side. Defaults to 1 (enabled).

session.use_only_cookies boolean

session.use_only_cookies specifies whether the module will only use cookies to store the session id on the client side. Enabling this setting prevents attacks involved passing session ids in URLs. This setting was added in PHP 4.3.0. Defaults to 1 (enabled) since PHP 6.0.

session.cookie_lifetime integer

session.cookie_lifetime 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 0. See also session_get_cookie_params() and session_set_cookie_params().

Note: The expiration timestamp is set relative to the server time, which is not necessarily the same as the time in the client's browser.

session.cookie_path string

session.cookie_path specifies path to set in session_cookie. Defaults to /. See also session_get_cookie_params() and session_set_cookie_params().

session.cookie_domain string

session.cookie_domain specifies the domain to set in session_cookie. Default is none at all meaning the host name of the server which generated the cookie according to cookies specification. See also session_get_cookie_params() and session_set_cookie_params().

session.cookie_secure boolean

session.cookie_secure specifies whether cookies should only be sent over secure connections. Defaults to off. This setting was added in PHP 4.0.4. See also session_get_cookie_params() and session_set_cookie_params().

session.cookie_httponly boolean

Marks the cookie as accessible only through the HTTP protocol. This means that the cookie won't be accessible by scripting languages, such as JavaScript. This setting can effectively help to reduce identity theft through XSS attacks (although it is not supported by all browsers).

session.cache_limiter string

session.cache_limiter specifies cache control method to use for session pages (none/nocache/private/private_no_expire/public). Defaults to nocache. See also session_cache_limiter().

session.cache_expire integer

session.cache_expire specifies time-to-live for cached session pages in minutes, this has no effect for nocache limiter. Defaults to 180. See also session_cache_expire().

session.use_trans_sid boolean

session.use_trans_sid whether transparent sid support is enabled or not. Defaults to 0 (disabled).

Note: For PHP 4.1.2 or less, it is enabled by compiling with --enable-trans-sid. From PHP 4.2.0, trans-sid feature is always compiled. URL based session management has additional security risks compared to cookie based session management. Users may send a URL that contains an active session ID to their friends by email or users may save a URL that contains a session ID to their bookmarks and access your site with the same session ID always, for example.

session.bug_compat_42 boolean

PHP versions 4.2.3 and lower have an undocumented feature/bug that allows you to initialize a session variable in the global scope, albeit register_globals is disabled. PHP 4.3.0 and later will warn you, if this feature is used, and if session.bug_compat_warn is also enabled. This feature/bug can be disabled by disabling this directive.

session.bug_compat_warn boolean

PHP versions 4.2.3 and lower have an undocumented feature/bug that allows you to initialize a session variable in the global scope, albeit register_globals is disabled. PHP 4.3.0 and later will warn you, if this feature is used by enabling both session.bug_compat_42 and session.bug_compat_warn.

session.hash_function mixed

session.hash_function allows you to specify the hash algorithm used to generate the session IDs. '0' means MD5 (128 bits) and '1' means SHA-1 (160 bits).

Since PHP 6.0.0 it is also possible to specify any of the algorithms provided by the hash extension (if it is available), like sha512 or whirlpool. A complete list of supported algorithms can be obtained with the hash_algos() function.

Note: This was introduced in PHP 5.

session.hash_bits_per_character integer

session.hash_bits_per_character allows you to define how many bits are stored in each character when converting the binary hash data to something readable. The possible values are '4' (0-9, a-f), '5' (0-9, a-v), and '6' (0-9, a-z, A-Z, "-", ",").

Note: This was introduced in PHP 5.

url_rewriter.tags string

url_rewriter.tags specifies which HTML tags are rewritten to include session id if transparent sid support is enabled. Defaults to a=href,area=href,frame=src,input=src,form=fakeentry,fieldset=

Note: If you want HTML/XHTML strict conformity, remove the form entry and use the <fieldset> tags around your form fields.

The track_vars and register_globals configuration settings influence how the session variables get stored and restored.

Note: As of PHP 4.0.3, track_vars is always turned on.