WordPress REST API Custom Endpoint with URL Parameter

Question

I am trying to create a custom endpoint for the WordPress REST API and pass parameters through the URL.

The endpoint currently is:

/wp-json/v1/products/81838240219

What I am trying to achieve is an endpoint that looks like this and being able to retrieve the identifier parameter in the callback.

/wp-json/v1/products?identifier=81838240219

// Custom api endpoint test
function my_awesome_func( $data ) {
  $identifier = get_query_var( 'identifier' );
  return $identifier;
}
add_action( 'rest_api_init', function () {
register_rest_route( 'api/v1', '/products=(?P<id>\d+)', array(
    'methods' => 'GET',
    'callback' => 'my_awesome_func',
  ) );
} );

Answer 1

First you need to pass in the namespace to register_rest_route

Like this

add_action( 'rest_api_init', function () {
    register_rest_route( 'namespace/v1', '/product/(?P<id>\d+)', array(
        'methods' => 'GET',
        'callback' => 'my_awesome_func',
    ) );
} );

Your name space namespace/v1 and your route is /product/{id} like this /namespace/v1/product/81838240219

and now you can use the route inside your function like this

function my_awesome_func( $data ) {
    $product_ID = $data['id'];
}

If you need to add options for ex. /namespace/v1/product/81838240219?name=Rob

and use it inside the function like this

function my_awesome_func( $data ) {
    $product_ID = $data['id'];
    $name = $data->get_param( 'name' );
}

The process is very simple but requires you to read this documentation