Get current user inside register_rest_route method - wordpress

Question

How to retrive wp_get_current_user() inside a register_rest_route callback (Wordpress site)?
I'm just trying to do a simple hello wp_get_current_user()->user_login on a php test page:
add_action('rest_api_init', 'helloTest');
function helloTest() {
register_rest_route('hello', 'hello/(?P<id>\d+)', array(
'methods' => WP_REST_SERVER::READABLE,
'callback' => 'showHello'
));
}
function showHello($someVariable) {
echo "Hello " . wp_get_current_user()->user_login . $someVariable;
}
But wp_get_current_user() is null and wp_get_current_user->ID is 0;
I dont want to authenticate the user again. I just want to retrieve his username. If he is not logged in, just show empty an empty string.
If I have to authenticate again, how to add a "nonce" to it? On internet I just have examples using javascript, but not directly on PHP methods.

Answer 1

Issues in your code
First off, you should understand properly how to add custom WP REST API endpoints:
An endpoint's namespace (the first parameter passed to register_rest_route()) should be in this format: your-plugin/v<version>. E.g. hello/v1 or hello-world/v1 and not just hello or hello-world.
$someVariable (the first parameter passed to your endpoint callback function) is not just any variable — it's an instance of the WP_REST_Request class — and shouldn't be echo-ed like what you did here:
function showHello($someVariable) {
echo "Hello " . wp_get_current_user()->user_login . $someVariable;
}
And normally, the $someVariable is better be changed to $request (i.e. rename it to "request").
And you should return a valid WP REST API response. For example, to return just the username:
return new WP_REST_Response( wp_get_current_user()->user_login, 200 );
And know your own API endpoint URL..
(based on your original namespace)
/wp-json/hello/hello/1 <- correct
/wp-json/hello/?John <- incorrect
because in your code, the parameter is a number and not string: (?P<id>\d+)
I hope those help you, and once again, do read the handbook for a more detailed guide.
The Corrected Code
add_action( 'rest_api_init', 'helloTest' );
function helloTest() {
register_rest_route( 'hello/v1', 'hello/(?P<id>\d+)', array(
'methods' => WP_REST_SERVER::READABLE,
'callback' => 'showHello'
) );
}
function showHello( $request ) {
return new WP_REST_Response( wp_get_current_user()->user_login, 200 );
}
Now about getting the user (from the API endpoint — showHello())
If I have to authenticate again, how to add a "nonce" to it?
Just because the user is logged-in/authenticated to the (WordPress) site, it doesn't mean the user is automatically logged-in to the WP REST API. So yes, you'd need to either provide a nonce along with your API request, or use one of the authentication plugins mentioned right here.
Now in most cases, GET (i.e. read-only) requests to the API do not need any authentication, but if you'd like to retrieve the data of the currently logged-in user on your site, then one way is via the _wpnonce data parameter (either POST data or in the query for GET requests).
Example for a GET request:
http://example.com/wp-json/wp/v2/posts?_wpnonce=<nonce>
So based on your comment and the corrected code (above):
Theres no "code" that make the request. Its is just an anchor that
calls my route: Hello
You can add the nonce as part of the URL query string like so: (the namespace is hello/v1 and the <id> is 1)
// Make request to /wp-json/hello/v1/hello/<id>
$nonce = wp_create_nonce( 'wp_rest' );
echo 'Hello';
So try that out along with the corrected code and let me know how it goes. :)
And once again, be sure to read the REST API authentication handbook.