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function site_fix_authordiv() {
        // wp-admin/post-new.php
        if ( !isset($_GET['post_type']) ) {
                $post_type = 'post';
        }
 
        elseif ( in_array( $_GET['post_type'], get_post_types( array('show_ui' => true ) ) ) ) {
                $post_type = $_GET['post_type'];
        }
        else {
                wp_die( __('Invalid post type') );
        }
 
        // wp-admin/edit-form-advanced.php
        if ( post_type_supports($post_type, 'author') ) {
                $post_type_object = get_post_type_object( $post_type );
 
                if ( is_super_admin() || current_user_can( $post_type_object->cap->edit_others_posts ) ) {
                        remove_meta_box( 'authordiv', 'tip', 'normal' );
                        add_meta_box('site-authordiv', __('Author'), 'site_fix_post_author_meta_box', 'tip', 'normal', 'core');
                }
        }
}
 
// wp-admin/includes/meta-boxes.php
function site_fix_post_author_meta_box($post) {
        global $user_ID;
?>
<label class="screen-reader-text" for="post_author_override"><?php _e('Author'); ?></label>
<?php
        wp_dropdown_users( array(
                'name' => 'post_author_override',
                'selected' => empty($post->ID) ? $user_ID : $post->post_author,
                'include_selected' => true
        ) );
}
 
add_action( 'add_meta_boxes', 'site_fix_authordiv' );