php man page for session_id

SESSION_ID(3)								 1							     SESSION_ID(3)

session_id - Get and/or set the current session id

SYNOPSIS
       string session_id ([string  $id])

DESCRIPTION
       session_id(3) 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.

PARAMETERS
	      o $id
		- If $id is specified, it will replace the current session id. session_id(3) needs to be called before session_start(3)  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)!

	      Note

		      When using session cookies, specifying an $id for session_id(3) will always send	a  new	cookie	when  session_start(3)	is
		     called, regardless if the current session id is identical to the one being set.

RETURN VALUES
       session_id(3)  returns  the session id for the current session or the empty string ( "") if there is no current session (no current session
       id exists).

SEE ALSO
       session_regenerate_id(3), session_start(3), session_set_save_handler(3), session.save_handler.

PHP Documentation Group 													     SESSION_ID(3)