Filtros personalizados de marca y stock

custom-filters-woocommerce.php

<?php

// Set query vars
add_filter('query_vars', 'dcms_add_query_vars');
function dcms_add_query_vars($query_vars) {
    $query_vars[] = "dcms-stock";
    $query_vars[] = "dcms-brand";

    return $query_vars;
}

// Modify main query
add_filter('posts_clauses', 'dcms_filter_query_categories');
function dcms_filter_query_categories($posts_clauses) {
    global $wpdb;

    if ( ! is_admin() && is_woocommerce() && (is_product_category() || is_product_tag())) {

        $stock = get_query_var('dcms-stock');
        $brand = get_query_var('dcms-brand');

        // If brand is selected
        if ( $brand ){
            $posts_clauses['join'] .= " INNER JOIN {$wpdb->prefix}term_relationships trs ON ( trs.object_id = $wpdb->posts.ID)
                                        INNER JOIN {$wpdb->prefix}term_taxonomy tt ON (trs.term_taxonomy_id = tt.term_taxonomy_id)";
            $posts_clauses['where'] .= " AND tt.term_id = $brand ";
        }

        // If stock is selected
        if ( $stock ){
            $posts_clauses['join'] .= " INNER JOIN {$wpdb->prefix}postmeta spm ON ( spm.post_id = $wpdb->posts.ID) ";
            if ( $stock === 'stock'){
                $posts_clauses['where'] .= " AND spm.meta_key = '_stock_status' AND spm.meta_value = 'instock'";
            } else if ( $stock === 'no-stock'){
                $posts_clauses['where'] .= " AND spm.meta_key = '_stock_status' AND spm.meta_value = 'outofstock'";
            }
        }

    }

    return $posts_clauses;
}

// Process filter forms
add_action( 'admin_post_nopriv_process_dcms_filter', 'dcms_process_filter' );
add_action( 'admin_post_process_dcms_filter', 'dcms_process_filter' );

function dcms_process_filter(){
    $stock = $_POST['dcms-filter-stock']??'';
	$brand = $_POST['dcms-filter-brands']??'';
    $url = $_POST['current_url']??'';

    wp_redirect( add_query_arg(['dcms-stock' => $stock, 'dcms-brand' => $brand], $url));
}

// Build filter Html form
add_action('woocommerce_archive_description', 'dcms_show_filters');

function dcms_show_filters(){
    global $wp;
    $current_url = add_query_arg( $wp->query_string, '', home_url( $wp->request ) );

    if ( is_product_category() ){
        echo "<form class='dcms-filters' method='post' action='".admin_url( 'admin-post.php' )."'>";
        dcms_show_filter_brand();
        dcms_show_filter_stock();
        echo "<input type='hidden' name='current_url' value='{$current_url}'>";
        echo "<input type='hidden' name='action' value='process_dcms_filter'>";
        echo "<input type='submit' name='submit' value='Filtrar'>";
        echo "</form>";
    }
}

// Html filter stock
function dcms_show_filter_stock(){
    $stock_var = get_query_var('dcms-stock');

    echo "<label for='dcms-filter-stock'>Stock: </label>";
    echo "<select class='dcms-filter-stock' name='dcms-filter-stock'>";
    echo "<option value=''>Todos</option>";
    echo "<option value='stock' " . ( $stock_var=='stock'?'selected':'') . ">Sólo existencias</option>";
    echo "<option value='no-stock' " . ( $stock_var=='no-stock'?'selected':'') . ">Sin stock</option>";
    echo "</select>";
}

// Html filter brand
function dcms_show_filter_brand(){
    $category_id = get_queried_object_id();
    $brands = dcms_get_brands_category($category_id);

    $brand_var = get_query_var('dcms-brand');

    if ( count($brands) > 0){
        echo "<label for='dcms-filter-brands'>Marcas: </label>";
        echo "<select class='dcms-filter-brands' name='dcms-filter-brands'>";
            echo "<option value=''>Todos</option>";
            foreach ($brands as $brand) {
                $selected = $brand_var == $brand->term_id ? 'selected' : '';
                echo "<option value='{$brand->term_id}' {$selected}>{$brand->name}</option>";
            }
        echo "</select>";
    }
}

// DB Query brands currenty category
function dcms_get_brands_category( $category_id ){
    global $wpdb;
    $sql = "SELECT DISTINCT t.term_id, t.name
            FROM {$wpdb->prefix}posts p
            INNER JOIN {$wpdb->prefix}term_relationships prs ON p.ID = prs.object_id
            INNER JOIN {$wpdb->prefix}term_relationships prsb ON p.ID = prsb.object_id
            INNER JOIN {$wpdb->prefix}term_taxonomy tt ON prsb.term_taxonomy_id = tt.term_taxonomy_id
            INNER JOIN {$wpdb->prefix}terms t ON tt.term_id = t.term_id
            WHERE
            p.post_status = 'publish'
            AND prs.term_taxonomy_id = {$category_id}
            AND tt.taxonomy = 'product_brand'";
    return $wpdb->get_results($sql);
}