ivanchaquea

update: ading these 2 conditions the backend and post page problems are fixed

add_filter ('pre_get_posts', 'mostrar_testimonios' );
function mostrar_testimonios( $query ) {
	    if ( is_category() ||  !is_admin()  && $query->is_category_page )
	        $query->set( 'post_type', array( 'post', 'testimonios' ) );
	    return $query;
	}

but the wp_nav_menu keeps dissapearing on the target page ( categories in my case)

edit: im using the default workdpress categories i created one category with a sub category, added some entries to the main category and then added my custom post type to the sub category. then i needed to display those subcategory items on my page. this is the updated code:

// create post type: testimonios
add_action('init', 'post_type_testimonios');
add_filter( 'pre_get_posts', 'mostrar_testimonios'  );

function post_type_testimonios() {

    register_post_type(
        'testimonios',
        array(
            'label' => __('Testimonios'),
            'description' => __('Ingresa un testimonio de  pacientes.'),
            'public' => true,
             'show_ui' => true,
               'capability_type' => 'post',
               'hierarchical' => false,
               'rewrite' => true,
               'query_var' => true,
            'menu_position' => 15,
            'supports' => array (
                'title',
                'editor',
                'thumbnail',
                'custom-fields',
                'categories'),
                'taxonomies' => array('post_tag','category')
        )
    );
 register_taxonomy_for_object_type('category', 'external');
 register_taxonomy_for_object_type('post_tag', 'external');

}
function mostrar_testimonios( $query ) {
        if ( is_category()  )
            $query->set( 'post_type', array( 'post', 'testimonios' )  );
        return $query;
    }

and it works as expected, the custom post type ( testimonios) is displaying well on its sub category. but, when i navigate on any category page, the wp_nav_menu() fails to load. its printing the cointainer div and the uls but none of the link items.

if i change or add any other page type to the line if ( is_category() ), like is_home(), or is_single() the menu will stop working on those too.

im also getting this error while navigating the categories panel on the backend

Warning: Illegal offset type in isset or empty in /home/public_html/wp/wp-includes/post.php on line 736

wish dissapears when i comment these lines :

add_filter( 'pre_get_posts', 'mostrar_testimonios'  );

function mostrar_testimonios( $query ) {
         if ( is_category()  )
             $query->set( 'post_type', array( 'post', 'testimonios' )  );
         return $query;
     }

im not sure what other function could i use to add these posts to the loop without needing to set more queries into it, or would that be the only choice for it?