function _reflow()
{
// PHP is broken yet again. Sort the arrays to remove the
// hole in the numeric indexes that make up the array.
$old_keys = $this->keys;
$old_values = $this->values;
$this->keys = array();
$this->values = array();
foreach ($old_keys as $k) {
$this->keys[] = $k;
}
foreach ($old_values as $v) {
$this->values[] = $v;
}
}