How to display Common posts from specific Tag & Category with Shortcode

Question

How to display posts that are common in Category A and Tag A, and I want to display posts by shortcode so that the Shortcode can be used on multiple locations with different category Ids and Tags.

I found the below code by google but don't know how to implement it in functions.php and not sure how to use it in the shortcode. I want to display Post Title, And Some Custom Field Value [For Example - Value A, Value B] in a table structure.

        $args = array(
        'category__and' => 'category', //must use category id for this field
        'tag__in' => 'post_tag', //must use tag id for this field
        'posts_per_page' => -1); //get all posts
        $posts = get_posts($args);
        foreach ($posts as $post) :
       //do stuff 
        endforeach;```

Answer 1

function common_cats($att){
 $args = array(
        'category__and' => $att['category'], //must use category id
        'tag__in' => $att['tag'], //must use tag id for this field
        'posts_per_page' => $att['posts_per_page']); //get all posts
        $posts = get_posts($args);
        $output = "<ul>";
        foreach ($posts as $post) :
           $output .= "<li>".get_the_title(). "</li>";
        endforeach;
        $output .= "</ul>"; 
return $output;
}
add_shortcode('commoncats', 'common_cats');

use [commoncats] where you like to show the output of the above code. above code will return a list of titles.