Child resource identification mapping to object 

Say we have a the following route ```/users/:id/comments/:comment_id```
The comments resource would have the identifier ```comment_id``` 

But given the structure of my entity
```php
class Comment
{
    public $id;
    public $user;
    public $comment;
}
```
The self link would fail due to the fact it searches the ```Comment``` object for ```comment_id``` when it's actually represented as ```id```