XML-RPC: Add category to post data

Question

I have a service that puts a daily post to my blog via XML-RPC. It doesn't offer me any control of what category it goes into so I want to just add a filter/hook to add the category I want into the incoming post data:

add_action ('xmlrpc_call', 'check_xmlrpc_call' );

function check_xmlrpc_call( $method )
{
    if( 'wp.newPost' === $method )
    {
        add_filter( 'xmlrpc_wp_insert_post_data', 'add_xmlrpc_category_post_data' );
    }
}

function add_xmlrpc_category_post_data( $post_data )
{
    //not sure how to add category to the post data :(

    return $post_data;  
}    

I think something like this in my functions.php would work? I just am not sure the correct format to add a category to the post data?

Maybe this?

$post_data['terms'] = array('category' => array(207))

Answer 1

Assigning posts to taxonomy terms in XML-RPC:

Let's assume your setup is:

                                     xml-rpc
                                    wp.newPost
                  (sender) site A -------------> site B (receiver)

and you want to assign the new posts to a given taxonomy terms on site B.

From site B:

Then you can try the following, on the receiving site B:

$post_data['tax_input'] = array( 'category' => array( 207 ) );

where the category taxonomy with id 207 already exists on the site B.

It's also possible to use the other supported parameters of wp_insert_post(), like post_category or tags_input. In your case you could therefore also use:

$post_data['post_category'] = array( 207 );

From site A:

Notice that the terms and terms_names parameters are supported by the payload of the wp.newPost query, from the sending site A.

Here's an example for the site A, how one could add terms of a given taxonomy:

$result = $client->query( 
    'wp.newPost', 
    array(
        $blog_id,
        $user,
        $password,
        array(
            'post_status'  => 'draft',
            'post_title'   => 'Test',
            'post_content' => 'We are testing XML-RPC!',
            'terms_names'  => array( 
                'post_tag' => array( 'xml-rpc' ), 
                'category' => array( 'wordpress-testing' ),
            ),
        )
    )
);