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# session_id

(PHP 4, PHP 5)

session_id -- Get and/or set the current session id

## 说明

string session_id ( [string id] )

session_id() is used to get or set the session id for the current session.

The constant SID can also be used to retrieve the current name and session id as a string suitable for adding to URLs. Note that SID is only defined if the client didn't send the right cookie. See also Session handling.

## 参数

id

  If id is specified, it will replace the current session id. session_id() needs to be called before session_start() for that purpose. Depending on the session handler, not all characters are allowed within the session id. For example, the file session handler only allows characters in the range a-z, A-Z and 0-9!

  > 注: When using session cookies, specifying an id for session_id() will always send a new cookie when session_start() is called, regardless if the current session id is identical to the one being set.

## 返回值

session_id() returns the session id for the current session or the empty string ("") if there is no current session (no current session id exists).

## 参见

session_regenerate_id()
session_start()
session_set_save_handler()
session.save_handler

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session_get_cookie_params | 上一级 | session_is_registered