session_id

Get and/or set the current session id

&reftitle.description; ``string``false```session_id` ``string``null```id`&null;

`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.

&reftitle.parameters;

`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-z A-Z 0-9 , (comma) and - (minus)`!

  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.

&reftitle.returnvalues;

`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.

&reftitle.changelog;

&Version; | &Description;
8.0.0 | `id` is nullable now.

&reftitle.seealso;

- `session_regenerate_id`
- `session_start`
- `session_set_save_handler`
- session.save_handler