So it turns out this was completely changed in 5.7 and the documentation has, unhelpfully, not been updated to reflect that. More info in the Git commit. Instead of: /wp-json/wp/v2/posts?tags=22,23&tax_relation=AND This URL works: /wp-json/wp/v2/posts?tags[terms]=22,23&tags[operator]=AND
The author parameter in your request, seems to be mapped to the author__in parameter in WP_Query that runs behind the rest-api call here, where a comma separated input: /wp-json/wp/v2/posts?author=1,5 is translated to an array( 1,5 ) input for author__in.
New user signup via REST API
WP Remote Request not returning all of content via request
Rest API code to get ID of current user not working: get_current_user_id() gives 0
Cannot add custom field to “orderby” parameter in Rest API
Is there builtin way to use protected AJAX endpoint?
Yes, it’s surely possible, but not out-of-the-box. I.e. There’s no such REST query parameter in the WordPress core, but you can add it to your REST API request, e.g. via the URL query string, and then use the rest_<post type>_query hook which “Filters WP_Query arguments when querying posts via the REST API” and “Enables adding … Read more
How can I create ‘future’ and ‘past’ parameter for restAPI by filtering the CPT custom date field by greater than / less than current datetime?
This is how I solved similar issue using validate callback – this is the part of code where bar argument is defined: ‘bar’ => array( ‘default’ => FALSE, ‘validate_callback’ => function($param, $request, $key) { if ($request[‘foo’] == 3) return ($param !== FALSE); return FALSE; } ), The default parameter causes call of validate callback even … Read more