missing <?php

@paolovas thanks for reporting this. You are right and those opening tags are missing.

However, instead of a "bug", this is considered a "feature" of the docs. It was decided a while ago to remove all the opening and closing PHP tags in the examples of the docs. In the past we've received some issues and some pull requests similar to this one and they were always rejected for not considering those tags strictly necessary for the code snippets shown in the docs.

The good news is that we added this feature to Symfony so you get an error message when the opening tag is missing.

For these reasons, I'm closing this pull request as "won't fix". I'm sorry.