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 "PHPSESSID" PHP_INI_ALL  
session.save_handler "files" PHP_INI_ALL  
session.auto_start "0" PHP_INI_PERDIR  
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_strict_mode "0" PHP_INI_ALL Available since PHP 5.5.2.
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 5.4.0.
session.bug_compat_warn "1" PHP_INI_ALL Available since PHP 4.3.0. Removed in PHP 5.4.0.
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.
session.upload_progress.enabled "1" PHP_INI_PERDIR Available since PHP 5.4.0.
session.upload_progress.cleanup "1" PHP_INI_PERDIR Available since PHP 5.4.0.
session.upload_progress.prefix "upload_progress_" PHP_INI_PERDIR Available since PHP 5.4.0. "PHP_SESSION_UPLOAD_PROGRESS" PHP_INI_PERDIR Available since PHP 5.4.0.
session.upload_progress.freq "1%" PHP_INI_PERDIR Available since PHP 5.4.0.
session.upload_progress.min_freq "1" PHP_INI_PERDIR Available since PHP 5.4.0.
For further details and definitions of the PHP_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 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.


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 64^3 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.

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. 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 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. 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 is available from PHP 5.5.4. 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 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 potentially cleaned up. Garbage collection may occur during session start (depending on session.gc_probability and session.gc_divisor).


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. This feature is supported on Windows since PHP 5.3.3. Setting session.entropy_length to a non zero value will make PHP use the Windows Random API as entropy source.

Note: As of PHP 5.4.0 session.entropy_file defaults to /dev/urandom or /dev/arandom if it is available. In PHP 5.3.0 this directive is left empty by default.

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_strict_mode boolean
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 ID. If uninitialized session ID is sent from browser, new session ID is sent to browser. Applications are protected from session fixation via session adoption with strict mode. 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 5.3.0.
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().


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 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 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 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: 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 5.3.0 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.


This setting 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, "-", ",").


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.

session.upload_progress.enabled boolean
Enables upload progress tracking, populating the $_SESSION variable. Defaults to 1, enabled.
session.upload_progress.cleanup boolean
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 integer
The minimum delay between updates, in seconds. Defaults to "1" (one second).

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

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 mor details on this functionality.


As of PHP 4.0.3, track_vars is always turned on.

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User Contributed Notes 12 notes

hassankhodadadeh at NOSPAM dot gmail dot com
2 years ago
max value for "session.gc_maxlifetime" is 65535. values bigger than this may cause  php session stops working.
00 at f00n dot com
6 years ago
After having many problems with garbage collection not clearing my sessions I have resolved it through the following.

First I found this in the php.ini (not something i noticed as i use phpinfo(); to see my hosting ini).

; NOTE: If you are using the subdirectory option for storing session files
;       (see session.save_path above), then garbage collection does *not*
;       happen automatically.  You will need to do your own garbage

; collection through a shell script, cron entry, or some other method. ;       For example, the following script would is the equivalent of
;       setting session.gc_maxlifetime to 1440 (1440 seconds = 24 minutes):
;          cd /path/to/sessions; find -cmin +24 | xargs rm

With this is mind there are options.

1. dont use a custom save_path.
** This means if your isp hasnt defaulted your session temp to something safer than install default or you are using a shared directory for session data then you would be wise to use named sessions to keep your session from being viewable in other people's scripts.  Creating a unique_id name for this is the common method. **

2. use your custom folder but write a garbage collection script.

3. use a custom handler and a database
4 years ago
apparently the default value for session.use_only_cookies has changed in 5.3.3 from 0 to 1. If you haven't set this in your php.ini or your code to 0 transparent sessions won't work.
3 years ago
This is how I set my session.save_path
session.save_path = "1;/home/askapache/tmp/s"
So to create the folder structure you can use this compatible shell script, if you want to create with 777 permissions change the umask to 0000;
sh -o braceexpand -c "umask 0077;mkdir -p s/{0..9}/{a..z} s/{a..z}/{0..9}"

Then you can create a cronjob to clean the session folder by adding this to your crontab which deletes any session files older than an hour:
@daily find /home/askapache/tmp/s -type f -mmin +60 -exec rm -f {} \; &>/dev/null

That will create sessions in folder like:

I don't think any non-mega site will need to go more than 1 levels deep.  Otherwise you create so many directories that it slows the performance gained by this.
11 days ago
We found a session.save_path depth of 3 led to excessive wastage of inodes and in fact disk space in storing the directory tree. dir_indexes option on ext2/3/4 makes larger directories more feasible anyway, so we decided to move to a depth of 2 instead.

It took a little puzzling to figure out how to move the existing PHP sessions up one directory tree, but we ended up running this in the root sessions directory:

for a in ./* ; do
    cd ./$a
    for b in ./* ; do
      cd ./$b
      # Move existing sessions out
      find ./* -xdev -type f -print0 | xargs -0 mv -t .
      # Remove subdirectories
      find ./* -xdev -type d -print0 | xargs -0 rmdir
      cd ..
  cd ..

This script may not be the best way to do it, but it got the job done fast. You can modify it for different depths by adding or removing "for" loops.

The documentation gives a depth of 5 as an example, but five is right out. If you're going beyond 2, you're at the scale where you may want to to look at a large memcached or redis instance instead.
Christopher Kramer
22 days ago
On debian (based) systems, changing session.gc_maxlifetime at runtime has no real effect. Debian disables PHP's own garbage collector by setting session.gc_probability=0. Instead it has a cronjob running every 30 minutes (see /etc/cron.d/php5) that cleans up old sessions. This cronjob basically looks into your php.ini and uses the value of session.gc_maxlifetime there to decide which sessions to clean (see /usr/lib/php5/maxlifetime).

You can adjust the global value in your php.ini (usually /etc/php5/apache2/php.ini). Or you can change the session.save_path so debian's cronjob will not clean up your sessions anymore. Then you need to either do your own garbage collection with your own cronjob or enable PHP's garbage collection (php then needs sufficient privileges on the save_path).

Why does Debian not use PHP's garbarage collection?
For security reasons, they store session data in a place (/var/lib/php5) with very stringent permissions. With the sticky bit set, only root is allowed to rename or delete files there, so PHP itself cannot clean up old session data. See .
jlevene at etisoftware dot com
1 year ago
Being unable to find an actual copy of, and seeing lots of complaints/bug fix requests for it, here's one that works.  It gets all its parameters from PHP.INI, so you don't have the opportunity to mess up:

# Creates directories for PHP session storage.
# Replaces the one that "comes with" PHP, which (a) doesn't always come with it
# and (b) doesn't work so great.
# This version takes no parameters, and uses the values in PHP.INI (if it
# can find it).
# Works in OS-X and CentOS (and probably all other) Linux.
# Feb '13 by Jeff Levene.

[[ $# -gt 0 ]] && echo "$0 requires NO command-line parameters.
It gets does whatever is called for in the PHP.INI file (if it can find it).
" && exit 1

# Find the PHP.INI file, if possible:
phpIni=/usr/local/lib/php.ini                        # Default PHP.INI location
[[ ! -f "$phpIni" ]] && phpIni=/etc/php.ini            # Secondary location
[[ ! -f "$phpIni" ]] && phpIni=                        # Found it?

# Outputs the given (as $1) parameter from the PHP.INI file:
# The "empty" brackets have a SPACE and a TAB in them.
PhpConfigParam() {
    [[ ! "$phpIni" ]] && return
    # Get the line from the INI file:
    varLine=`grep "^[     ]*$1[     ]*=" "$phpIni"`

    # Extract the value:
    value=`expr "$varLine" : ".*$1[     ]*=[     ]*['\"]*\([^'\"]*\)"`
    echo "$value"

if [[ "$phpIni" ]]
    savePath=`PhpConfigParam session.save_path`
    # If there's a number and semicolon at the front, remove them:
    dirDepth=`expr "$savePath" : '\([0-9]*\)'`
    [[ "$dirDepth" ]] && savePath=`expr "$savePath" : '[0-9]*;\(.*\)'` || dirDepth=0
    bits=`PhpConfigParam session.hash_bits_per_character`
    case "x$bits" in
        x)    echo "hash_bits_per_character not defined.  Not running." ; exit 2 ;;
        x4) alphabet='0 1 2 3 4 5 6 7 8 9 a b c d e f' ;;
        x5) alphabet='0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v' ;;
        x6) alphabet='0 1 2 3 4 5 6 7 8 9 a b c d e f g h i j k l m n o p q r s t u v'
            alphabet="$alphabet w x y z A B C D E F G H I J K L M N O P Q R S T U V W"
            alphabet="$alphabet X Y Z - ,"
        *)    echo "unrecognized hash_bits_per_character.  Not running." ; exit 2 ;;
    echo "Cannot find the PHP.INI file.  Not running.  Sorry."
    exit 2

# The depth of directories to create is $1.  0 means just create the named
# directory.  Directory to start with is $2.
# Used recursively, so variables must be "local".

doDir() {
    local dir="$2"
    if [[ -d "$dir" ]]
        echo "Directory '$dir' already exists.  No problem."
    elif [[ -f "$dir" ]]
        echo "FILE '$dir' exists.  Aborting." ; exit 2
        if mkdir "$dir"
            echo "Directory '$dir' created."
            echo "Cannot create directory '$dir'.  Aborting." ; exit 2
    chmod a+rwx "$dir"
    if [[ $1 -gt 0 ]]
        local depth=$(( $1 - 1 ))
        for letter in $alphabet
        do    doDir $depth "$dir/$letter"
echo "Running with savePath='$savePath', dirDepth=$dirDepth, and bitsPerCharacter=$bits."
sleep 3

doDir $dirDepth "$savePath"

exit 0
mikaelkael at php dot net
5 years ago
Recently, I needed to change the session save_path in my program under Windows. With an ini_set('session.save_path', '../data/sessions'); (and session.gc_divisor = 1 for test), I always obtain 'Error #8 session_start(): ps_files_cleanup_dir: opendir(../data/sessions) failed: Result too large'.

I corrected this by changing with ini_set('session.save_path', realpath('../data/sessions'));
4 years ago
Transient sessions do not appear to be working in 5.3.3


("session.use_cookies", 0);
ini_set("session.use_trans_sid", 1);
    if (isset(
$_SESSION["foo"])) {
"Foo: " . $_SESSION["foo"];
    } else {
$_SESSION["foo"] = "Bar";
"<a href=?" . session_name() . "=" . session_id() . ">Begin test</a>";

This works in 5.2.5, but not 5.3.3
4 years ago
When setting the session.cookie_lifetime directive in a .htaccess use string format like;

php_value session.cookie_lifetime "123456"

and not

php_value session.cookie_lifetime 123456

Using a integer as stated above dit not work in my case (Apache/2.2.11 (Ubuntu) PHP/5.2.6-3ubuntu4.5 with Suhosin-Patch mod_ssl/2.2.11 OpenSSL/0.9.8g)
sony-santos at bol dot com dot br
6 years ago
In response to 00 at f00n, this very page explains:

"(...) if N is used and greater than 0 then automatic garbage collection will not be performed (...)"

So you can actually use custom save_path with automatic garbage collection, since you don't use the subdirectory option (that N subdirectory levels).
phpforcharity dot 5 dot pistos at geoshell dot com
6 years ago
To get session IDs to show up in URIs, and not get stored via cookies, you must not only set session.use_cookies to 0, but also set session.use_trans_sid to 1.  Otherwise, the session ID goes neither in a cookie nor in URIs!
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