session_id()

session_id() — Get and/or set the current session 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. See also Session handling.

Inputs: id: If id is specified and not null, 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-zA-Z0-9,-]!

Returns: 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). On failure, false is returned.