How can I show second most recent post in sidebar, if most recent post is open in the browser?

Question

I am working on an online magazine in WordPress PHP. I created a custom post type (article) with 4 available custom categories. In the sidebar I want to show the most recent post of all the 4 categories. But if one of the most recent articles are actually open in the browser, I want the sidebar to show the second most recent article in the given category to avoid recurrence. I got to the point where I extracted the slug from the browser url and the slug of the latest post from the given category, but I stopped there. I think I should use an if statement, but I don't quite know how. I appreciate all help, thank you.

sidebar-right.php (this is just one query of the 4 in the sidebar, I repeat this code for all 4 categories):

    <?php

    global $post;
    $post_slug_open = $post->post_name;

    ?>

    <div class="sidebar-preview-container">
        <?php
        // Define our WP Query Parameters
        $the_query = new WP_Query(array(
            'post_type' => 'articles',
            'post_status' => 'publish',
            'posts_per_page' => 1,
            'orderby' => 'date',
            'order'   => 'DESC',
            'tax_query' => array(
                array(
                    'taxonomy' => 'article_category',
                    'field' => 'slug',
                    'terms' => 'interju',
                )
            ),
        ));
        ?>

        <?php
        // Start our WP Query
        while ($the_query->have_posts()) : $the_query->the_post();
            // Display the Post Title with Hyperlink
            $article_categories = get_the_terms(get_the_ID(), 'article_category');
            $article_title = get_field("article_title");
            $article_subtitle = get_field('article_subtitle');
            $article_preview_image = get_field('article_preview_image');
            $article_slug = get_post_field('post_name', get_post());

            setup_postdata($post);
            ?>

            <div class="sidebar-article-preview">
                <?php
                    if ($article_categories) :
                        foreach ($article_categories as $article_category) :
                            ?>
                        <a href="<?php echo get_stylesheet_directory_uri(); ?>/<?php echo $article_category->slug; ?>">
                            <h6 class="article-category-preview">
                                <?php echo $article_category->name; ?>
                                <?php echo  $article_slug; ?>
                            </h6>
                        </a>
                <?php
                        endforeach;
                    endif;
                    ?>

                <a href="<?php the_permalink() ?>">
                    <h4 class="article-title-preview">
                        <?php the_title(); ?>
                    </h4>
                </a>

                <p class="article-subtitle-preview">
                    <?php echo $article_subtitle; ?>
                </p>

                <a href="<?php echo get_permalink(); ?>">
                    <img class="article-preview-img" src="<?php echo $article_preview_image['url']; ?>" alt="<?php echo $article_preview_image['alt']; ?>">
                </a>
            </div>
````````````````

Answer 1

You can use the WP Query option "post__not_in" for that, this variable should be an array with IDs of posts that should not appear on the result, so you would use it like that:

$the_query = new WP_Query(array(
        'post__not_in' => array( get_the_ID() ),
        'post_type' => 'articles',
        'post_status' => 'publish',
        'posts_per_page' => 1,
        'orderby' => 'date',
        'order'   => 'DESC',
        'tax_query' => array(
            array(
                'taxonomy' => 'article_category',
                'field' => 'slug',
                'terms' => 'interju',
            )
        ),
    ));

Note that, the get_the_ID() will retrieve the ID of the most recent post from a loop, so you may need to retrieve the ID of the post early and use it instead of the get_the_ID()