How to define a query parameter with REST API?

I’m trying to define a GET REST API endpoint with register_rest_route

register_rest_route supports defining a URL parameter and it is documented at https://developer.wordpress.org/rest-api/extending-the-rest-api/adding-custom-endpoints/#arguments

I would love to define a list of query parameters and let WordPress handle the validation part. Is there an official way to do so?

Answers:

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Method 1

Yes, from the link you posted there are examples for both sanitising and validating the parameters. Validating does a check which can fail and block the API call from running; sanitising just does some operations to clean or interpret the parameter and does not stop the API call from running.

An example of validation, taken from the page:

<?php
add_action( 'rest_api_init', function () {
  register_rest_route( 'myplugin/v1', '/author/(?P<id>d+)', array(
    'methods' => 'GET',
    'callback' => 'my_awesome_func',
    'args' => array(
      'id' => array(
        'validate_callback' => function($param, $request, $key) {
          return is_numeric( $param );
        }
      ),
    ),
  ) );
} );

You can see in the second parameter of register_rest_route that this defines an endpoints like /author/1234

The format of the second parameter of register_rest_route breaks down as:

• /author/ initial part of the URL to match
• ?P a code specific to this function that means ‘parameter’. Note this is not included in the URL when called
• <id> optional name for the parameter, used belows in args, not included as part of URL.
• d+ the regex for this parameter

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0