Using Config Variables Inside Environment Files

[kmgdevelopment]

I've been trying to set some variables on a per-environment basis inside Master Config, but I keep getting browser errors. For example, if I put this at the bottom of config.local.php:

if ($site_id == '1') {
    $env_config['webmaster_email'] = '[email protected]';
} else {
    $env_config['webmaster_email'] = '[email protected]';
}

I get a browser "can't load this page" error.

What am I doing wrong here?