get_posts works in the page template but not in a shortcode

Question

I am trying to write a shortcode, which includes 'get_posts' in order to get the blog posts data and then display the 3 most recent on the page.

This code works within the template. However, when I put it into a shortcode, within output buffering (ob_start), it fails to retrieve the posts. Instead, it takes the current page itself and loops through that instead (in this case the homepage).

Any idea how I can get it to loop through the posts as originally intended?

Here is the code that works in the template:

<?php $lastposts = get_posts( array('posts_per_page' => 3) );?>
<?php if ( $lastposts ) {
    foreach ( $lastposts as $post ) :
        setup_postdata( $post ); ?>
        <div class="single_post" onclick="location.href = '<?php the_permalink(); ?>';">
            <div class="postbox" style="background-image: url('<?php echo catch_first_image() ?>');">
                <div class="pink_cover">
                    <div class="text-center datebox">
                        <h5><?php the_time('j'); ?></h5>
                        <hr>
                        <h6><?php the_time('M'); ?></h6>
                        <h6><?php the_date('Y'); ?></h6>
                    </div>
                </div>
            </div>
            <div class="row infobox">
                <div class="col-9">
                    <h3><a href="<?php the_permalink(); ?>"><?php the_category($separator = ', '); ?></a></h3>
                    <h4><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h4>
                </div>
                <div class="col-3 infobox-moreinfo">
                    <img src="more_info.png">
                </div>
            </div>
        </div>
    <?php endforeach; wp_reset_postdata(); } ?>

Here is the shortcode that, while displays something similar on the page, does not retrieve the blog posts themselves.

add_shortcode('home_blog', function(){
    ob_start();
    ?>
        <?php $lastposts = get_posts( array('posts_per_page' => 3) );?>
            <?php if ( $lastposts ) {
                foreach ( $lastposts as $post ) :
                    setup_postdata( $post ); ?>
                    <div class="single_post" onclick="location.href = '<?php the_permalink(); ?>';">
                        <div class="postbox" style="background-image: url('<?php echo catch_first_image() ?>');">
                            <div class="pink_cover">
                                <div class="text-center datebox">
                                    <h5><?php the_time('j'); ?></h5>
                                    <hr>
                                    <h6><?php the_time('M'); ?></h6>
                                    <h6><?php the_date('Y'); ?></h6>
                                </div>
                            </div>
                        </div>
                        <div class="row infobox">
                            <div class="col-9">
                                <h3><a href="<?php the_permalink(); ?>"><?php the_category($separator = ', '); ?></a></h3>
                                <h4><a href="<?php the_permalink(); ?>"><?php the_title(); ?></a></h4>
                            </div>
                            <div class="col-3 infobox-moreinfo">
                                <img src="more_info.png">
                            </div>
                        </div>
                    </div>
                <?php endforeach; wp_reset_postdata(); } ?>
        <?php
        $output = ob_get_clean();
        return $output;
});

Answer 1

You might be missing global $post before the foreach loop in your shortcode function. Please refer to the setup_postdata codex entry.