Ошибка при авторизации

function get_rd($sess_id = 0) // Advanced internal redirect by yura3d
{
$rd = (isset($_SESSION['rd']) && $_SESSION['rd'] != '') ? $_SESSION['rd'] : 'index.php';
if (!$sess_id) {return $rd;}
preg_match('#([^\?]+|)(\?([^\#]+)|)(\#(.*)|)#s', $rd, $rd);
if ($rd[3] === '') {$rd[3] = '?'._SESSION_ID;}
else {$rd[3] = $rd[2].'&'._SESSION_ID;}
if ($rd[5] !== '') {$rd[5] = $rd[4];}
return $rd = $rd[1].$rd[3].$rd[5];
}

if ($rd[5] !== '') {$rd[5] = $rd[4];}

$rd[5] = (count($rd) == 6 && $rd[5] !== '') ? $rd[4] : '';