function expand_all(&$expanded)
{
  // mark all threads with children as to be shown expanded
  $conn = db_connect();
  $query = 'select postid from header where children = 1';
  $result = mysql_query($query);
  $num = mysql_numrows($result);
  for($i = 0; $i<$num; $i++)
  {
    $expanded[mysql_result($result, $i, 0)]=true;
  } 
}