Load custom post type with ID in a shortcode

Question

I developed a theme for the first time. I created a custom post type for banners/call to actions that I want to include in different posts with a shortcode. The shortcode should look like: [banner id=123].

Until now, all banners are shown, and the parameter of my shortcode doesn't filter the results. Where is my failure?

 function mrt_shortcode_banner( $atts ) {
        // Attributes
        $atts = shortcode_atts(
            array(
                'bannerid' => null,            ),
            $atts,
            'banner'
        );       

        $mrt_load_banner = new WP_Query( array(
            'post_type' => 'banner',
            'p' => $bannerid ,            
        ) ); 

        if ( $mrt_load_banner->have_posts() ) { 
          while ( $mrt_load_banner->have_posts() ) { $mrt_load_banner->the_post(); ?>
                   <?php the_content(); ?>
            <?php 
             }
        } else {
          return 'Nothing found';
        }
        wp_reset_postdata();
    }
add_shortcode( 'banner', 'mrt_shortcode_banner' );

I have tested by typing the ID as a numeric value in the function: ('p' => 123). This worked fine. So I guess I have to specify the bannerid in another way. But I don't know how. Thanks for your hints!

Answer 1

Okay, I solved my issue - it was too easy.

I replaced

'p' => $bannerid,  

with

'p' => $atts['bannerid'],  

Now I am happy :)