Related Posts: Changing Function For Posts Per Page

Question

I am working on dailysuit.de, which features 8 related articles below the content in every post, defined by some tags.

Now I wanted to reduce the number of "posts per page" from 8 to 4. Of course, I can easily achieve that by changing the functions.php, but as soon as the theme gets an update, the figure is back to 8.

So, I wanted to change the function and add it to the child theme's functions.php:

/* Related posts */
function longform_the_related_posts_change() {
global $post;
$tags = wp_get_post_tags($post->ID);

if ($tags) {
    $tag_ids = array();

    foreach($tags as $individual_tag) {
        $tag_ids[] = $individual_tag->term_id;
    }

    $args = array(
        'tag__in'             => $tag_ids,
        'post__not_in'        => array($post->ID),
        'posts_per_page'      => 4, // Number of related posts to display.
        'ignore_sticky_posts' => 1
    );

    $my_query = new wp_query( $args ); ?>

    <h2 class="related-articles-title"><?php _e( 'Related articles', 'longform' ); ?></h2>
    <div class="related-articles">
        <?php
        while( $my_query->have_posts() ) {
            $my_query->the_post(); ?>

            <div class="related-thumb col-sm-3 col-md-3 col-lg-3">
                <a rel="external" href="<?php the_permalink(); ?>">
                    <?php the_post_thumbnail(array(500,350)); ?>
                    <div class="related-content">
                        <h2><?php the_title(); ?></h2>
                    </div>
                </a>
            </div>
        <?php } ?>
        <div class="clearfix"></div>
    </div>
<?php
}
wp_reset_postdata();
wp_reset_query();
}
add_filter( 'longform_the_related_posts', 'longform_the_related_posts_change' );

Unfortunately, that did not work. It still shows 8 relates posts instead of the 4, that I entered at "posts_per_page".

Anyone knows what is wrong there? Or is there a easier/shorter way without copying all this code?

I also tried the remove_filter thing, that was mentioned, but that did not work out either.

longform_the_related_posts_child () {
remove_filter('longform_the_related_posts');
add_filter('longform_the_related_posts', array(
    'longform_the_related_posts_filter' => 'longform_the_related_posts',
    'posts_per_page' => 4,
) );
}

Answer 1

I have gone through your code and found that the function longform_the_related_posts displays 8 related posts. This function is defined in functions.php of parent theme and called in single.php.

Thus, to override the function, follow below steps -
1. Create another function that displays 4 related posts in functions.php of child theme. (As you have already created function longform_the_related_posts_change() )
2. Copy the file single.php from parent to child theme and replace the line 47

From

echo longform_the_related_posts();

To

echo longform_the_related_posts_change();

This would call the function that display 4 posts.
Hope this helps.

Answer 2

The above code looks okay. I think the reason why you are getting 8 posts instead of 4 is that, you still have a code that fetches 8 posts in parent theme's functions.php.

Try removing filter of parent theme in child theme. Like this -

remove_filter('<filter_name>','<function_name>');

By doing this, parent themes's function would not take effect and child theme's code would work.

For more info on remove_filter - https://codex.wordpress.org/Function_Reference/remove_filter

Hope this helps.