(PHP 4, PHP 5, PHP 7)
posix_getsid — Get the current sid of the process
$pid
   ) : int
   Return the session id of the process pid.
   The session id of a process is the process group id of the session leader.
  
pid
       The process identifier. If set to 0, the current process is
       assumed.  If an invalid pid 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 integer.
Example #1 Example use of posix_getsid()
<?php
$pid = posix_getpid();
echo posix_getsid($pid); //8805
?>