session_name

    (PHP 4, PHP 5, PHP 7, PHP 8)

    session_name — Get and/or set the current session name

    Description

    session_name(?string $name = null): string|false

    session_name() returns the name of the current session. If name is given, session_name() will update the session name and return the old session name.

    If a new session name is supplied, session_name() modifies the HTTP cookie (and output content when session.transid is enabled). Once the HTTP cookie is sent, session_name() raises error. session_name() must be called before session_start() for the session to work properly.

    The session name is reset to the default value stored in session.name at request startup time. Thus, you need to call session_name() for every request (and before session_start() is called).

    Parameters

    name

    The session name references the name of the session, which is used in cookies and URLs (e.g. PHPSESSID). It should contain only alphanumeric characters; it should be short and descriptive (i.e. for users with enabled cookie warnings). If name is specified and not null, the name of the current session is changed to its value.

    Warning

    The session name can't consist of digits only, at least one letter must be present. Otherwise a new session id is generated every time.

    Return Values

    Returns the name of the current session. If name is given and function updates the session name, name of the old session is returned, or false on failure.

    Changelog

    Version Description
    8.0.0 name is nullable now.
    7.2.0 session_name() checks session status, previously it only checked cookie status. Therefore, older session_name() allows to call session_name() after session_start() which may crash PHP and may result in misbehaviors.

    Examples

    Example #1 session_name() example

    <?php

    /* set the session name to WebsiteID */

    $previous_name = session_name("WebsiteID");

    echo     "The previous session name was $previous_name<br />";
    ?>

    See Also

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    User Contributed Notes 9 notes

    up
    144
    Hongliang Qiang
    20 years ago
    This may sound no-brainer: the session_name() function will have no essential effect if you set session.auto_start to "true" in php.ini . And the obvious explanation is the session already started thus cannot be altered before the session_name() function--wherever it is in the script--is executed, same reason session_name needs to be called before session_start() as documented.

    I know it is really not a big deal. But I had a quite hard time before figuring this out, and hope it might be helpful to someone like me.
    up
    62
    php at wiz dot cx
    15 years ago
    if you try to name a php session "example.com" it gets converted to "example_com" and everything breaks.

    don't use a period in your session name.
    up
    38
    relsqui at chiliahedron dot com
    15 years ago
    Remember, kids--you MUST use session_name() first if you want to use session_set_cookie_params() to, say, change the session timeout. Otherwise it won't work, won't give any error, and nothing in the documentation (that I've seen, anyway) will explain why.

    Thanks to brandan of bildungsroman.com who left a note under session_set_cookie_params() explaining this or I'd probably still be throwing my hands up about it.
    up
    21
    Joseph Dalrymple
    13 years ago
    For those wondering, this function is expensive!

    On a script that was executing in a consistent 0.0025 seconds, just the use of session_name("foo") shot my execution time up to ~0.09s. By simply sacrificing session_name("foo"), I sped my script up by roughly 0.09 seconds.
    up
    10
    Victor H
    8 years ago
    As Joseph Dalrymple said, adding session_name do slow down a little bit the execution time.
    But, what i've observed is that it decreased the fluctuation between requests.
    Requests on my script fluctuated between 0,045 and 0,022 seconds. With session_name("myapp"), it goes to 0,050 and 0,045. Not a big deal, but that's a point to note.

    For those with problems setting the name, when session.auto_start is set to 1, you need to set the session.name on php.ini!
    up
    2
    mmulej at gmail dot com
    3 years ago
    Hope this is not out of php.net noting scope.

    session_name('name') must be set before session_start() because the former changes ini settings and the latter reads them. For the same reason session_set_cookie_params($options) must be set before session_start() as well.

    I find it best to do the following.

    function is_session_started()
    {
    if (php_sapi_name() === 'cli')
    return false;

    if (version_compare(phpversion(), '5.4.0', '>='))
    return session_status() === PHP_SESSION_ACTIVE;

    return session_id() !== '';
    }
    if (!is_session_started()) {
    session_name($session_name);
    session_set_cookie_params($cookie_options);
    session_start();
    }
    up
    -1
    tony at marston-home dot demon dot co dot uk
    6 years ago
    The description that session_name() gets and/or sets the name of the current session is technically wrong. It does nothing but deal with the value originally supplied by the session.name value within the php.ini file.

    Thus:-
    $name = session_name();
    is functionally equivalent to
    $name = ini_get('session.name');
    and
    session_name('newname);
    is functionally equivalent to
    ini_set('session.name','newname');

    This also means that:
    $old_name = session_name('newname');
    is functionally equivalent to
    $old_name = ini_set('session.name','newname');

    The current value of session.name is not attached to a session until session_start() is called. Once session_start() has used session.name to lookup the session_id() in the cookie data the name becomes irrelevant as all further operations on the session data are keyed by the session_id().

    Note that changing session.name while a session is currently active will not update the name in any session cookie. The new name does not take effect until the next call to session_start(), and this requires that the current session, which was created with the previous value for session.name, be closed.
    up
    -3
    tony at marston-home dot demon dot co dot uk
    6 years ago
    The description has recently been modified to contain the statement "When new session name is supplied, session_name() modifies HTTP cookie". This is not correct as session_name() has never modified any cookie data. A change in session.name does not become effective until session_start() is called, and it is session_start() that creates the cookie if it does not already exist.

    See the following bug report for details: https://bugs.php.net/bug.php?id=76413
    up
    -3
    descartavel1+php at gmail dot com
    1 year ago
    Always try to set the prefix for your session name attribute to either `__Host-` or `__Secure-` to benefit from Browsers improved security. See https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie#attributes

    Also, if you have auto_session enabled, you must set this name in session.name in your config (php.ini, htaccess, etc)
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