基于自定义字段对特定产品的折扣

Question

I want a discount 11% on specific products that have a published year after 2016 in my woocommerce eshop.

This field (pub_year) is a custom field in a custom table with the name fancyplugin_wc_product_info in the wpdb.

I tried some code(which is a mixed code from a research I made) with no success.

The code that I tried:

function get_price_multiplier() {
    return 100; // 100 the multiplier
}

function get_price_discount() {
    return 11; // 11% discount
}  

add_filter('woocommerce_product_get_price', 'custom_price', 99, 2 );
add_filter('woocommerce_product_get_sale_price', 'custom_price', 99, 2 ); 
function custom_price( $price, $product ) { 
    global $woocommerce, $post, $wpdb; 

    $table_name = $wpdb->prefix . 'fancyplugin_wc_product_info'; 

    $result = ("SELECT * FROM {$table_name} WHERE pub_year >= '2016'"); 

    if( $result ) { 
        $price = $price - (get_price_discount() / get_price_multiplier() * $price); 
    } 
    return $price; 
} 

Answer 1

Your SQL query using WPDB class is incomplete and wrong… As the column for product ID in the table wp_fancyplugin_wc_product_info is post_id, you need to query it for the current product ID… Try the following instead:

function process_sale_price( $price ) {
    $percentage = 11; // 11% discount

    return ( 100 - $percentage ) / 100 * $price;
}

add_filter('woocommerce_product_get_price', 'custom_price', 99, 2 );
add_filter('woocommerce_product_get_sale_price', 'custom_price', 99, 2 );
function custom_price( $price, $product ) {
    global $wpdb;

    $result = $wpdb->get_var( $wpdb->prepare("
        SELECT post_id FROM {$wpdb->prefix}fancyplugin_wc_product_info
        WHERE pub_year >= '2016' AND post_id = %d
    ", $product->get_id() ) );

    if( ! empty($result) ) {
        return process_sale_price( $price );
    }
    return $price;
}

Code goes in functions.php file of your active child theme (or active theme). It should work.