XML-RPC: Add category to post data

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' ),
            ),
        )
    )
);