(PHP 4 >= 4.3.0, PHP 5)
pg_get_pid — Gets the backend's process ID
$connection
   )pg_get_pid() gets the backend's (database server process) PID. The PID is useful to determine whether or not a NOTIFY message received via pg_get_notify() is sent from another process or not.
connectionPostgreSQL database connection resource.
The backend database process ID.
Example #1 PostgreSQL backend PID
<?php 
$conn = pg_pconnect("dbname=publisher");
if (!$conn) {
  echo "An error occurred.\n";
  exit;
}
// Backend process PID. Use PID with pg_get_notify()
$pid = pg_get_pid($conn);
?>