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).
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.
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.
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.
|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.|