Having problems with user defined sessions using postgresql as my session manager

[Richmond Dyes <rdyes@xxxxxxxxxxxxxx>]

I have written user defined session management library in php using postgresql as my session repository.  When I let my session timeout on my browser I get the below errors on my screen.

   Warning: pg_query(): Query failed: ERROR: duplicate key violates unique constraint "li_session_pkey" in /var/www/html/liberty/includes/session.php on line 31

Fatal error: Call to undefined function: pg_error() in /var/www/html/liberty/includes/session.php on line 31

Warning: Unknown(): A session is active. You cannot change the session module's ini settings at this time. in Unknown on line 0

The problem is in the write function of my library. Here it is:

function pg_session_write($sid, $val) {
    $life = get_cfg_var("session.gc_maxlifetime");
    $exp = time() + $life;
    $selQ = "SELECT sidid FROM li_session
    WHERE sidid = '$sid' AND exptime >". time();
    $selR= pg_query($selQ)or die("It didn't work:". pg_error());
     if(pg_num_rows($selR)) {
        $sesupQ ="UPDATE li_session SET
        exptime = '$exp', vidval = '$val'
        WHERE
        sidid = '$sid' and exptime >". time();
        $sesupR=pg_query($sesupQ) or die("It didn't work:". pg_error());
    } else {
     $sesinQ = "INSERT INTO li_session
    VALUES('$sid', '$val', '$exp')";
    $sesinR= pg_query($sesinQ) or die("It didn't work:". pg_error());   
    }
}