display a random post thumbnail from a random category

Question

I have 2 categories in my cutom post type: Cat 1 Cat 2

I wish display a random category from this post type. I made this and it works:

function categorie(){    
    $global;    
    $args = array('type' => 'carte', 'taxonomy' => 'carte-category', 'parent' => 0);
    $categories = get_categories($args);
    shuffle( $categories);
    $i = 0;

    foreach($categories as $category) {
        $i++;
        $categoryname=  $category->name;
        $html.= '<h3> '. $category->name. '</h3>';
        $html.= '<p class="txtContent"> '. $category->description. '</p>'; 

        if (++$i == 2) break;
    }

    return $html;
}

add_shortcode( 'categorie', 'categorie' );

But now in this random category, I wish display a thumbnail from random post

To be clear:

Cat1 = Menus Posts: Menu 1, menu 2...

Cat 2 = Dishes Posts: Dish 1, Dish 2...

If my random cat is displaying Cat1, I need the thumbnail of Menu 1 or Menu 2

How can I do that ?

Answer 1

All you need to do is to add another query in your code:

function categorie_shortcode_callback() {    
    $html = '';
    $categories = get_categories( array(  
        // 'type' => 'carte', <- THERE IS NO ATTRIBUTE CALLED type FOR get_categories, SO REMOVE THAT
        'taxonomy' => 'carte-category',
        'parent' => 0
    ));
    shuffle( $categories);

    // you also don't need to loop through that array, since you only want to get first one
    if ( ! empty($categories) ) {
        $category = $categories[0];
        $html.= '<h3> '. $category->name. '</h3>';
        $html.= '<p class="txtContent"> '. $category->description. '</p>'; 

        $random_posts = get_posts( array(
            'post_type' => 'carte',
            'posts_per_page' => 1,
            'orderby' => 'rand',
            'fields' => 'ids',
            'tax_query' => array(
                array( 'taxonomy' => 'carte-category', 'terms' => $category->term_id, 'field' => 'term_id' )
            )
        ) );
        if ( ! empty($random_posts) ) {
            $html .= get_the_post_thumbnail( $random_posts[0] );
        }
    }

    return $html;
}
add_shortcode( 'categorie', 'categorie_shortcode_callback' );

Answer 2

Inser this inside foreach loop:

$args_query = array(
    'order'          => 'DESC',
    'orderby'        => 'rand',
    'posts_per_page' => 1,
    'cat' => $category->term_id,
);

$query = new WP_Query( $args_query );

if( $query->have_posts() ) {
    while( $query->have_posts() ) {
        $query->the_post();
        the_post_thumbnail();
    }
} else {
    echo 'No post found';
}

wp_reset_postdata();