woocommerce-related-posts.php

<?php
/**
 * Change related products output
 */ 
add_filter( 'woocommerce_related_products', 'pd_related_products_by_series_and_brand', 9999, 3 ); 
function pd_related_products_by_series_and_brand( $related_posts, $product_id, $args ) {
	// set up query args
	$argsarray = array(
	   'post_type' 		=> 'product',
	   'post_status' 	=> 'publish',
	   'posts_per_page'	=> 4,
	   'exclude' 		=> $product_id
	);
	
	
	// Get series terms
	$series_terms = get_the_terms( $product_id, 'series' );
	if ( !empty( $series_terms ) ){
	    // get the first term
	    $term = array_shift( $series_terms );
	    $series = $term->slug;
	}
	
	// Get brands terms
	$brands = get_the_terms( $product_id, 'brand' );
	if ( !empty( $brands ) ){
	    // get the first term
	    $term = array_shift( $brands );
	    $brand = $term->slug;
	}
	
	$terms = wp_get_post_terms($product_id, 'product_cat');
    foreach ( $terms as $term ) $cats_array[] = $term->term_id;
	
	// Check if there are series or brands taxonomies. If not, default to tags and categories
   if($series || $brand){
	   
		$series_query = array(
			'relation' => 'OR',
            'series_query' => array(
                'taxonomy'     => 'series',
                'field'        => 'slug',
                'terms'        => $series
            ),
            'brand_query' => array(
                'taxonomy'     => 'brand',
                'field'        => 'slug',
                'terms'        => $brand
            )
        );   
   	 	$argsarray['tax_query'] = $series_query;
   } else {
	    
	    // Get Categories
	    $terms = wp_get_post_terms($product_id, "product_cat");
	    foreach ( $terms as $term ) $cats_array[] = $term->term_id;
	    
	    // Set the default query
		$cat_query = array(
            array(
                'taxonomy'     => 'product_cat',
                'field'        => 'id',
                'terms'        => $cats_array
            )
        );
		$argsarray['tax_query'] = $cat_query;
   }
   
   // Modify the standard Related Post Query
   $related_posts = get_posts( $argsarray );
   
   // If returned amount is less than desired 4, query category as well and merge arrays
   if( $related_posts->found_posts < 4 ){
	   
	   // set the new limit to 4 minus the amount of already returned posts
	    $newLimit = 4 - count($related_posts);
		
		$argsarray['posts_per_page'] = $newLimit;
		
		// get the categories
	    $terms = wp_get_post_terms($product_id, "product_cat");
		foreach ( $terms as $term ) $cats_array[] = $term->term_id;
		
		$cat_query = array(
			array(
				'taxonomy'     => 'product_cat',
				'field'        => 'id',
				'terms'        => $cats_array
			)
		);
		
		// set the args up
		$argsarray['tax_query'] = $cat_query;
		// query the posts
	   $newquery = get_posts( $argsarray );
	   
	   // merge the array
	   $related_posts = array_merge( $newquery, $related_posts );
	}
   
   // return the array of posts
   return $related_posts;
}
?>