By default, tasks are launched only with the project - this means that they do not have access to your settings in app.yml. You either need to:
explicitly pass the application parameter every time you call the task, this is done as:
php symfony ns:task --application=frontend
add it as the default parameter in configure() :
$this->addOptions(array( new sfCommandOption('application', "app", sfCommandOption::PARAMETER_REQUIRED, 'The application name', "frontend") ));
Maerlyn
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