wp_query display posts from same category of the post

Question

On my post page I am trying to display list of other posts from the same category of the original post. So far I got this and this does not seem to work:

<?php

    $args = array(
        'post_type' => 'article',
        'posts_per_page' => 5,
        'post__not_in' => array( get_the_ID() ),
        'category'     => array( get_the_category() ),
        'meta_query' => array(
                    array(
                    'key' => 'recommended_article',
                    'value' => '1',
                    'compare' => '=='
                        )
                    )
    );
    $query = new WP_Query( $args );

?>

    <?php if( $query->have_posts() ) : while( $query->have_posts() ) : $query->the_post(); ?>

<a class="popup-article-picture" href="<?php the_permalink(); ?>" style="background-image: url('<?php the_post_thumbnail_url(); ?>');"></a>
<a class="popup-article-title" href="<?php the_permalink(); ?>"><?php the_title(); ?></a>

    <?php endwhile; endif; wp_reset_postdata(); ?>

Answer 1

I've found an answer:

<?php

    $cats = get_the_category();
    $args = array(
        'post_type' => 'article',
        'post__not_in' => array( get_the_ID() ),
        'posts_per_page' => 5,
        'cat'     => $cats[0]->term_id,
        'meta_query' => array(
                    array(
                    'key' => 'recommended_article',
                    'value' => '1',
                    'compare' => '=='
                        )
                    )
    );
    $query = new WP_Query( $args );

?>  

<?php if( $query->have_posts() ) : while( $query->have_posts() ) : $query->the_post(); ?>   

<!--HTML-->

<?php endwhile; endif; wp_reset_postdata(); ?>

Answer 2

you are trying to query the custom post type called article. are you using default WordPress post categories for post type article? or have registered any custom taxonomy for that post type? i assume you are using default WordPress category for CPT. so first step is to get the current category from single page. following function will return categories attached to the post from outside the loop.

get_the_category();

it will return an array of term objects. and you have to get the slug from this array to pass in the query. lets assume we have only one category assigned for single post.

$category_obj = get_the_category();
$category = $category_obj[0]->slug;

now you can use that in your related posts query.

$args = array(
        'post_type' => 'article',
        'posts_per_page' => 5,
        'category'     => $category,
        'meta_query' => array(
                    array(
                    'key' => 'recommended_article',
                    'value' => '1',
                    'compare' => '=='
                        )
                    )
    );
    $query = new WP_Query( $args );

and if you are using custom taxonomy for post type then let us know so we can help you regarding custom taxonomies.