# dans application.ini

classe.implementation.adai=MyAdaiDB


# dans index.php

$classeAdai = $config->classe->implementation->adai;
require_once('adai/' .$adai .'.php'); // in libraries/adai
$registry->set('adai', new $classeAdai());


# dans MonAdapteurAuth.php

$registry = Zend_Registry::getInstance();
$adai = $registry->get('adai');  
if ($adai->estValide($this->identifiant, ''))
  ...
  
