Restricting results to the same category as the current post object

add_filter( 'asp_query_args', 'asp_posts_from_same_terms', 10, 2 );
function asp_posts_from_same_terms($args, $search_id) {
	$taxonomies = 'category, post_tag';	// comma separated list of taxonomies
	$allow_missing = false; // allow (empty) items with no connection to any of the taxonomy terms filter
  $search_ids = 'all';    // comma separated list of search IDs, where the code should apply
​
	// --- DO NOT CHANGE ANYTHING BELOW ---
    $search_ids = explode(',', $search_ids);
    foreach ( $search_ids as &$sid )
        $sid = trim($sid);
	if (
	        !empty($args['_page_id']) &&
            ( in_array('all', $search_ids) || in_array($search_id, $search_ids) )
    ) {
		$taxonomies = explode(',', $taxonomies);
		foreach ( $taxonomies as $taxonomy ) {
			$taxonomy = trim($taxonomy);
			$terms = wp_get_object_terms(
			    $args['_page_id'],
                $taxonomy,
                array('fields' => 'ids')
            );
			if ( !is_wp_error($terms) && count($terms) ) {
				$args['post_tax_filter'][] = array(
				  'taxonomy'  => $taxonomy, // taxonomy name
				  'include'   => $terms,   	// array of taxonomy term IDs to include
				  'exclude'   => array(),
				  'allow_empty' => $allow_missing    // allow (empty) items with no connection to any of the taxonomy terms filter
				);
			}
		}
	}
	return $args;
}