title: Symfony2: accessing variables defined in config.yml and config_*.yml
body: <p>Let's say I have a simple traditional contact form on my site and I would like it to use the subject "Test: (subject_field value)" in dev environment and "(subject_field_value)" in prod environment when sending e-mail. Is there a way to define a variable called "subject_prefix" in config_dev.yml and config_prod.yml and then just use something like <code>$this-&gt;get('config')-&gt;get('subject_prefix')</code>? I would expect that call to return "Test: (subject_field value)" in dev environment and "(subject_field_value)" in prod environment.</p>