WordPress: Display the posts of all categories, at most 5 posts per category, and ordered by date?

Question

I am not sure if this has been answered before, but vigorous googling has not led me anywhere so far.

I have a wordpress site where I would like to display all posts as usual, ordered by date. However, instead of setting a limit on the total number of posts displayed, I would like to set a limit on each category.

For instance, if I have two categories FOO and BAR, I want WordPress to display all, but at most 5, posts from both FOO and BAR. The posts should still be ordered by date, and I mean that any post from FOO that was posted before one from BAR appears first and vice versa.

Specific problem: There is one post in the category FOO from last year, then 20 entries in BAR since then and now I am adding another post in the category FOO. Usually, Wordpress with a post limit of 10 would display this most recent FOO entry and 9 more BAR entries. However, I would like it to display both my FOO entries and the 5 most recent BAR entries. Only after I add 4 more FOO entries, the FOO entry from last year will no longer be displayed.

What is the best, most clean and maintainable way to achieve this?

I would be very grateful for any help.

Answer 1

Given that there seems no other solution that doing an insane amount of queries, I devised the following, added to functions.php.

function alter_query( $query ) {
    if ( $query->is_home() && $query->is_main_query() ) {
        $post_limit = floor(get_settings('posts_per_page')/2);      
        $the_posts = array();
        foreach (get_terms('category',array('hide_empty'=>1,'fields'=>'ids')) as $id) 
            $the_posts = array_merge( $the_posts, 
                get_posts( array(
                    'fields'      => 'ids',
                    'numberposts' => $post_limit,
                    'category'    => $id, 
                    'orderby'     => 'post_date')));
        $query->set('post__in',    $the_posts);
        $query->set('numberposts', -1);
        $query->set('orderby',     'post_date');
    }
}
add_action( 'pre_get_posts', 'alter_query' );

In this solution, I only fetch the ids of all relevant posts first, instead of all the contents and then perform a query to retrieve the actual data. I prefer this solution so far because I can use it without even touching my main loop, which is modified via the hook pre_get_posts.

I would still prefer a solution that is a little faster, i.e. one that only performs a single query.

Answer 2

You just need to use get_categories, get_posts with order by date and use foreach to show the results.

Here is:

<?php
// Setting blank array
$posts_category = array();

// Getting categories
$args = array('type' => 'post', 'orderby' => 'name', 'hide_empty' => 1);
$categories = get_categories( $args ); // Getting all categories

foreach($categories as $category) {
          $counter = 1;

          // Getting posts
          $args = array('posts_per_page'=> 5, 'offset'=> 1, 'category' => $category->term_id, 'post_status' => 'publish', 'orderby' => 'date', 'order' => 'ASC');
          $posts = get_posts( $args ); // Getting all posts

          if(count($posts) >= 1) {
                    foreach($posts as $post) { // Register every post found
                              if(!array_key_exists($post->ID, $posts_category)) {
                                $posts_category[$post->ID] = array('title' =>$post->post_title, 'permalink' => get_permalink($post->ID), 'date' => $post->post_date);
                                $counter = $counter+1;
                              }
                    }
          }
}

// Sorting all posts by date
function sortByDate($a, $b) {
          return strtotime($a["date"]) - strtotime($b["date"]);
}
usort($posts_category, "sortByDate");
$posts = array_reverse($posts_category);

//Showing results
foreach($posts_category as $post) { ?>
<li>
          <a href="<?php echo $post['permalink']; ?>"><?php echo $post['title']; ?></a>
</li>
<?php }

Answer 3

Untested, but this should get you started:

$terms = get_terms('category');
$results = array(); //Initialize results array
foreach($terms as $term){
    $args = array(
        'posts_per_page'=>5,
        'tax_query' => array(
            array(
                'taxonomy' => 'category',
                'terms'    => $term->term_id,
            ),
        )
    );
    $q = new WP_Query($args);
    if($q->have_posts()) : while($q->have_posts()) : the_post();
        $results[] = $post->ID; //Append IDs to results
    endwhile;endif;
}
if($all_posts = array_unique($results)){ //Filter out the duplicates
    $q = new WP_Query(array('post__in'=>$all_posts)); //Query all results
    while($q->have_posts()) : the_post();
        //Loop markup goes here
    endwhile;
}
else{
    //No posts found
}