fix route prefix in PHP code example
minor #4353 [Cookbook][Controller] fix route prefix in PHP code example (xabbuh)

This PR was merged into the master branch.

Discussion
----------

[Cookbook][Controller] fix route prefix in PHP code example

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.6
| Fixed tickets |

Commits
-------

16daca4 fix route prefix in PHP code example