Loop any Post-Type in Specific Category

loop_all_in_cat.php

<?php

// Fetch all posts, regardless of post-type, in "my_category".
$args = array(
  'post_type'     => 'any',
  'category_name' => 'my_category'
);

// Call the $args ^ in a new WP_Query(). 
$the_query = new WP_Query( $args );

// The default loop is `if ( have_posts() ) : while ( have_posts() ) : the_post();`
// but after changing the query, we have to add $the_query-> before each hook.
if ( $the_query->have_posts() ) : while ( $the_query->have_posts() ) : $the_query->the_post(); 

/* Close the PHP tag */ ?>

<!-- The <article> post HTML here. Pretend. -->


<?php // More PHP

endwhile; // This closes the `while( $the_query->have_posts() )` condition.
endif; // This closes the `if( $the_query-> have_posts() )` condition.

// When you modify the loop, you have to "reset" it - otherwise your modifications might
// mess up what WP does out of the box.
wp_reset_postdata();
?>