Group blog posts by category boilerplate.

group-posts-by-cat.php

<?php
// get all the categories from the database
$cats = get_categories(); 

// loop through the categries
foreach ($cats as $cat) {
  // setup the cateogory ID
  $cat_id= $cat->term_id; ?>
 
  <h2><?php echo $cat->name ?></h2>

  <?php
  $args = array(
    'cat'              => $cat_id,
    'posts_per_page'   => 3
  );
  
  query_posts($args);
  // start the wordpress loop!
  if (have_posts()) : while (have_posts()) : the_post(); ?>

    <?php get_template_part('templates/post-module'); ?>

  <?php endwhile; endif; // done our wordpress loop. Will start again for each category ?>
<?php } // done the foreach statement ?>