Modify WordPress Rest Api Request/Response

Question

I am building an application using WordPress Rest API.

I want to make simple calls to the API, such as just /wp-json/wp/v2/posts and let the backend have a systematic way how to handle this and serve /wp-json/wp/v2/posts?per_page=7 under the hood instead.

Basically, how can I override the defaults for the Rest API responses without specifying them in the query string?

Again, I don't want to pass parameters in the query string. I need simple query strings and standardized responses.

This: WordPress Docs - Modifying Responses doesn't seem to cover my use case, it is to add fields and the like, which is not what I want to do. I'm looking for a way to hook into the request and alter it before returning a response.

So something a little before this hook: Rest API Hook When Post Is Requested perhaps?

I gather that the above hook has already gotten ready to serve the response, I want to hook in before that to change the request headers.

EDIT:

The closest filter I have found is : rest_request_from_url but it never seems to fire.

Furthermore, rest_pre_dispatch is filtering the response, not the request.

Is there nothing like this request reference for the Rest API?

If so, how do I alter the response without slowing down my server, since it will fetch 10 posts by default before I chop it down to however many I actually want.

Answer 1

I think I found answer to your question, it is: rest_{$this->post_type}_query filter hook. With this hook you are able to directly edit internal WP_Query parameter.

For example, if you'd like to internally sort Posts by post_title by default, then you'd have to write something like this:

function order_rest_post_by_post_title($args, $request) {
  $args['orderby'] = 'post_title';
  $args['order'] = 'DESC';

  return $args;
}
add_filter('rest_post_query', 'order_rest_post_by_post_title', 10, 2);

For more info please follow this link.

Answer 2

To define default values, you can use the filter rest_{$post_type}_collection_params like that :

$post_type = "post";

add_filter("rest_{$post_type}_collection_params", function ($query_params, $post_type) {

    $query_params["per_page"]["default"] = 7;

    return $query_params;

}, 10, 2);