DQL custom functions on doctrine reference page

Custom DQL functions can be configured in two ways, according to what I was told [ here ] (https://github.com/symfony/symfony-docs/pull/3939)

It should be clearified in doctrine reference page because It may confuse some people that just read the cookbook  section about [custom DQL functions] (http://symfony.com/doc/current/cookbook/doctrine/custom_dql_functions.html)
I'm not so sure about showing other formats too: 
- Yaml is more readable and shows what has to be done quite well. 
- PHP isn't even shown on this same page
- XML could be done, yes.

Anyway I'll work on that a bit later and I'll propose your recommendation too. Thanks!