@Marco, Matus: You are right. I ended up with:
$appConfig = require 'config/application.config.php';
if(getenv('APPLICATION_ENV') == 'development' AND
is_readable('config/application.config.local.php')){
$localAppConfig = require 'config/application.config.local.php';
$appConfig = array_merge_recursive($appConfig,$localAppConfig);
}
