(PHP 4, PHP 5, PHP 7, PHP 8)
posix_getsid — Get the current sid of the process
$process_id): int|false
   Return the session id of the process process_id.
   The session id of a process is the process group id of the session leader.
  
process_id
       The process identifier. If set to 0, the current process is
       assumed.  If an invalid process_id is
       specified, then false is returned and an error is set which
       can be checked with posix_get_last_error().
      
   Returns the identifier, as an int,  or false on failure.
  
Example #1 Example use of posix_getsid()
<?php
$pid = posix_getpid();
echo posix_getsid($pid); //8805
?>