Ah yes, correct. But isn't the fetch default is still needed since we're not setting it by default? (I think it just proxies to `Hash#fetch`):

```ruby
composer_version = fetch(:composer_version, nil)
composer_version_option = composer_version ? "-- --version=#{composer_version}" : ""
execute :curl, "-s", fetch(:composer_download_url), "|", :php, composer_version_option
```

`to_s` isn't needed with the empty string now.