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



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

session_name() は、現在のセッション名を返します。 name を渡すと、 session_name() はセッション名を上書きして 元の セッション名を返します。

新しいセッションの name が与えられると、 session_name() 関数は HTTPクッキー を 変更します(そして、session.transid が有効なときは、出力内容も変更します)。 HTTPクッキー が一度送信されると、 session_name() 関数はエラーになります。 session_name() 関数は、 セッションを適切に動作させるためには、 session_start() の前に呼び出さなければなりません。

リクエストが開始された際にセッション名はリセットされ、 に保存されたデフォルト値に戻ります。 よって、各リクエスト毎に(そして session_start() をコールする前に) session_name() をコールする必要があります。



セッションの名前を参照します。これは、クッキーや URL (例: PHPSESSID) で使われます。 セッション名は英数字のみで構成されている必要があり、また、 短く、その内容が分かるようなものである必要があります (これは、クッキー警告を有効にしているユーザー用です)。 name が指定され、null でない場合、 現在のセッションの名前が、指定された値に置き換えられます。


セッション名は数字だけで構成することはできません。 少なくとも文字がひとつ以上現れる必要があります。そうでない場合、 新規セッション ID が毎回生成されます。


現在のセッションの名前を返します。 name を渡すと、 session_name() はセッション名を上書きして 元のセッション名を返します。 失敗した場合に false を返します


バージョン 説明
7.2.0 name は、nullable になりました。
7.2.0 session_name() 関数は、 セッションの状態をチェックするようになりました。 これより前のバージョンでは、 クッキー の状態をチェックするだけでした。 そのため、古い session_name() 関数は session_start() 関数の後に session_name() 関数を呼び出すことを許して しまっており、それが PHP のクラッシュや不具合を起こす可能性がありました。

例1 session_name() の例


/* セッション名をWebsiteIDに設定する */

$previous_name = session_name("WebsiteID");

"前回のセッション名は $previous_name でした<br />";


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User Contributed Notes 10 notes

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.
php at wiz dot cx
15 years ago
if you try to name a php session "" it gets converted to "example_com" and everything breaks.

don't use a period in your session name.
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 who left a note under session_set_cookie_params() explaining this or I'd probably still be throwing my hands up about it.
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.
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 on php.ini!
mmulej at gmail dot com
3 years ago
Hope this is not out of 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()) {
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 value within the php.ini file.

$name = session_name();
is functionally equivalent to
$name = ini_get('');
is functionally equivalent to

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

The current value of is not attached to a session until session_start() is called. Once session_start() has used 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 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, be closed.
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 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:
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

Also, if you have auto_session enabled, you must set this name in in your config (php.ini, htaccess, etc)
slave at codegrunt dot com
19 years ago
One gotcha I have noticed with session_name is that it will trigger a WARNING level error if the cookie or GET/POST variable value has something other than alphanumeric characters in it. If your site displays warnings and uses PHP sessions this may be a way to enumerate at least some of your scripts:

Warning: session_start(): The session id contains invalid characters, valid characters are only a-z, A-Z and 0-9 in /some/path/foo.php on line 666

I did not see anything in the docs suggesting that one had to sanitize the PHP session ID values before opening the session but that appears to be the case.

Unfortunately session_name() always returns true so you have to actually get to the point of assigning variables values before you know whether you have been passed bad session data (as far as I can see). After the error has been generated in other words.

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