public function getClient($id)
{
if (!array_key_exists($id, $this->_clients)) {
throw new InvalidParamException("Unknown auth client '{$id}'.");
}
if (!is_object($this->_clients[$id])) {
$this->_clients[$id] = $this->createClient($id, $this->_clients[$id]);
}
return $this->_clients[$id];
}