The wording here implies that ".local.php" is a widely used convention, but as far as I know this is specific to ZF2? (Perhaps other PHP frameworks that I've not used also follow this.) 

I'd write this as:

> You'll notice that we didn't define a `username` or `password` in this config file. It's good practice to keep login details and other environment-specific data separate from other application configuration. This way these files can easily be excluded from source control, and easily modified for other installs of your application (for example on your production server). The Zend Framework skeleton application is setup to exclude any config files ending in `local.php` from source control. Let's make use of this by creating a config file that provides our credentials: