Runtime Configuration

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

Session configuration options
Name Default Changeable Changelog
session.save_path "" INI_ALL "PHPSESSID" INI_ALL  
session.save_handler "files" INI_ALL  
session.auto_start "0" INI_PERDIR  
session.gc_probability "1" INI_ALL  
session.gc_divisor "100" INI_ALL  
session.gc_maxlifetime "1440" INI_ALL  
session.serialize_handler "php" INI_ALL  
session.cookie_lifetime "0" INI_ALL  
session.cookie_path "/" INI_ALL  
session.cookie_domain "" INI_ALL  
session.cookie_secure "0" INI_ALL Prior to PHP 7.2.0, the default was "".
session.cookie_httponly "0" INI_ALL Prior to PHP 7.2.0, the default was "".
session.cookie_samesite "" INI_ALL Available as of PHP 7.3.0.
session.use_strict_mode "0" INI_ALL  
session.use_cookies "1" INI_ALL  
session.use_only_cookies "1" INI_ALL  
session.referer_check "" INI_ALL  
session.cache_limiter "nocache" INI_ALL  
session.cache_expire "180" INI_ALL  
session.use_trans_sid "0" INI_ALL  
session.trans_sid_tags "a=href,area=href,frame=src,form=" INI_ALL Available as of PHP 7.1.0.
session.trans_sid_hosts $_SERVER['HTTP_HOST'] INI_ALL Available as of PHP 7.1.0.
session.sid_length "32" INI_ALL Available as of PHP 7.1.0.
session.sid_bits_per_character "4" INI_ALL Available as of PHP 7.1.0.
session.upload_progress.enabled "1" INI_PERDIR  
session.upload_progress.cleanup "1" INI_PERDIR  
session.upload_progress.prefix "upload_progress_" INI_PERDIR "PHP_SESSION_UPLOAD_PROGRESS" INI_PERDIR  
session.upload_progress.freq "1%" INI_PERDIR  
session.upload_progress.min_freq "1" INI_PERDIR  
session.lazy_write "1" INI_ALL  
session.hash_function "0" INI_ALL Removed as of PHP 7.1.0.
session.hash_bits_per_character "4" INI_ALL Removed as of PHP 7.1.0.
session.entropy_file "" INI_ALL Removed as of PHP 7.1.0.
session.entropy_length "0" INI_ALL Removed as of PHP 7.1.0
For further details and definitions of the INI_* modes, see the Where a configuration setting may be set.

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, with a Windows version called mod_files.bat. 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.

The file storage module creates files using mode 600 by default. This default can be changed with the optional MODE argument: N;MODE;/path where MODE is the octal representation of the mode. Setting MODE does not affect the process umask.


If this is 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.


When using the optional directory level argument N, as described above, note that using a value higher than 1 or 2 is inappropriate for most sites due to the large number of directories required: for example, a value of 3 implies that (2 ** session.sid_bits_per_character) ** 3 directories exist on the filesystem, which can result in a lot of wasted space and inodes.

Only use N greater than 2 if you are absolutely certain that your site is large enough to require it. string 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 bool
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. PHP serialize format (name php_serialize), PHP internal formats (name php and php_binary) and WDDX are supported (name wddx). WDDX is only available, if PHP is compiled with WDDX support. php_serialize uses plain serialize/unserialize function internally and does not have limitations that php and php_binary have. Older serialize handlers cannot store numeric index nor string index contains special characters (| and !) in $_SESSION. Use php_serialize to avoid numeric index or special character errors at script shutdown. Defaults to php.
session.gc_probability int
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 int
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 int
session.gc_maxlifetime specifies the number of seconds after which data will be seen as 'garbage' and potentially cleaned up. Garbage collection may occur during session start (depending on session.gc_probability and session.gc_divisor). Defaults to 1440 (24 minutes).

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.

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. This feature is supported on Windows. Setting session.entropy_length to a non zero value will make PHP use the Windows Random API as entropy source.

Note: Removed in PHP 7.1.0. session.entropy_file defaults to /dev/urandom or /dev/arandom if it is available.

session.entropy_length int
session.entropy_length specifies the number of bytes which will be read from the file specified above. Defaults to 32. Removed in PHP 7.1.0.
session.use_strict_mode bool
session.use_strict_mode specifies whether the module will use strict session id mode. If this mode is enabled, the module does not accept uninitialized session IDs. If an uninitialized session ID is sent from the browser, a new session ID is sent to the browser. Applications are protected from session fixation via session adoption with strict mode. Defaults to 0 (disabled).

Note: Enabling session.use_strict_mode is mandatory for general session security. All sites are advised to enable this. See session_create_id() example code for more details.


If a custom session handler registered via session_set_save_handler() does not implement SessionUpdateTimestampHandlerInterface::validateId(), nor supplies the validate_sid callback, respectively, strict session ID mode is effectively disabled, regardless of the value of this directive. Particularly note that SessionHandler does not implement SessionHandler::validateId().

session.use_cookies bool
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 bool
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 that involve passing session IDs in URLs. Defaults to 1 (enabled).
session.cookie_lifetime int
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 the 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 the 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 bool
session.cookie_secure specifies whether cookies should only be sent over secure connections. With this option set to on, sessions only work with HTTPS connections. If it is off, then sessions work with both HTTP and HTTPS connections. Defaults to off. See also session_get_cookie_params() and session_set_cookie_params().
session.cookie_httponly bool
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.cookie_samesite string
Allows servers to assert that a cookie ought not to be sent along with cross-site requests. This assertion allows user agents to mitigate the risk of cross-origin information leakage, and provides some protection against cross-site request forgery attacks. Note that this is not supported by all browsers. An empty value means that no SameSite cookie attribute will be set. Lax and Strict mean that the cookie will not be sent cross-domain for POST requests; Lax will send the cookie for cross-domain GET requests, while Strict will not.
session.cache_limiter string
session.cache_limiter specifies the cache control method used for session pages. It may be one of the following values: nocache, private, private_no_expire, or public. Defaults to nocache. See also the session_cache_limiter() documentation for information about what these values mean.
session.cache_expire int
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 bool
session.use_trans_sid whether transparent sid support is enabled or not. Defaults to 0 (disabled).

Note: 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. Since PHP 7.1.0, full URL path, e.g., is handled by trans sid feature. Previous PHP handled relative URL path only. Rewrite target hosts are defined by session.trans_sid_hosts.

session.trans_sid_tags string
session.trans_sid_tags specifies which HTML tags are rewritten to include session id when transparent sid support is enabled. Defaults to a=href,area=href,frame=src,input=src,form= form is special tag. <input hidden="session_id" name="session_name"> is added as form variable.

Note: Before PHP 7.1.0, url_rewriter.tags was used for this purpose. Since PHP 7.1.0, fieldset is no longer considered as special tag.

session.trans_sid_hosts string
session.trans_sid_hosts specifies which hosts are rewritten to include session id when transparent sid support is enabled. Defaults to $_SERVER['HTTP_HOST'] Multiple hosts can be specified by ",", no space is allowed between hosts. e.g.,,
session.sid_length int
session.sid_length allows you to specify the length of session ID string. Session ID length can be between 22 to 256. The default is 32. If you need compatibility you may specify 32, 40, etc. Longer session ID is harder to guess. At least 32 chars are recommended.

Compatibility Note: Use 32 instead of session.hash_function=0 (MD5) and session.hash_bits_per_character=4, session.hash_function=1 (SHA1) and session.hash_bits_per_character=6. Use 26 instead of session.hash_function=0 (MD5) and session.hash_bits_per_character=5. Use 22 instead of session.hash_function=0 (MD5) and session.hash_bits_per_character=6. You must configure INI values to have at least 128 bits in session ID. Do not forget to set an appropriate value for session.sid_bits_per_character, otherwise you will have weaker session ID.

Note: This setting is introduced in PHP 7.1.0.

session.sid_bits_per_character int
session.sid_bits_per_character allows you to specify the number of bits in encoded session ID character. The possible values are '4' (0-9, a-f), '5' (0-9, a-v), and '6' (0-9, a-z, A-Z, "-", ","). The default is 4. The more bits results in stronger session ID. 5 is recommended value for most environments.

Note: This setting is introduced in PHP 7.1.0.

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).

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: Removed in PHP 7.1.0.

session.hash_bits_per_character int
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: Removed in PHP 7.1.0.

session.upload_progress.enabled bool
Enables upload progress tracking, populating the $_SESSION variable. Defaults to 1, enabled.
session.upload_progress.cleanup bool
Cleanup the progress information as soon as all POST data has been read (i.e. upload completed). Defaults to 1, enabled.

Note: It is highly recommended to keep this feature enabled.

session.upload_progress.prefix string
A prefix used for the upload progress key in the $_SESSION. This key will be concatenated with the value of $_POST[ini_get("")] to provide a unique index. Defaults to "upload_progress_". string
The name of the key to be used in $_SESSION storing the progress information. See also session.upload_progress.prefix. If $_POST[ini_get("")] is not passed or available, upload progressing will not be recorded. Defaults to "PHP_SESSION_UPLOAD_PROGRESS".
session.upload_progress.freq mixed
Defines how often the upload progress information should be updated. This can be defined in bytes (i.e. "update progress information after every 100 bytes"), or in percentages (i.e. "update progress information after receiving every 1% of the whole filesize"). Defaults to "1%".
session.upload_progress.min_freq int
The minimum delay between updates, in seconds. Defaults to "1" (one second).
session.lazy_write bool
session.lazy_write, when set to 1, means that session data is only rewritten if it changes. Defaults to 1, enabled.

Upload progress will not be registered unless session.upload_progress.enabled is enabled, and the $_POST[ini_get("")] variable is set. See Session Upload Progress for more details on this functionality.