Displaying the sale percentage on the Woocommerce admin table

display-sale-percentage.php

<?php
/**
 * Add a custom column for displaying the sale percentage in the WooCommerce Products admin table.
 *
 * @param array $columns Existing columns in the Products table.
 * @return array Modified columns with the Sale Percentage column added.
 */
function add_sale_percentage_column_to_products( $columns ) {
    // Add a new column for Sale Percentage
    $columns['sale_percentage'] = 'Sale Percentage';
    return $columns;
}
add_filter( 'manage_edit-product_columns', 'add_sale_percentage_column_to_products' );

/**
 * Display the sale percentage in the custom column for each product.
 *
 * @param string $column The name of the current column being rendered.
 * @param int $post_id The ID of the current product post.
 */
function display_sale_percentage_in_column( $column, $post_id ) {
    if ( $column === 'sale_percentage' ) {
        // Get the WooCommerce product object
        $product = wc_get_product( $post_id );
        
        if ( $product->is_type( 'variable' ) ) {
            // For variable products, calculate the average sale percentage across all variations
            $variations = $product->get_children(); // Get all variation IDs
            $total_percentage = 0;
            $count = 0;

            foreach ( $variations as $variation_id ) {
                $variation = wc_get_product( $variation_id ); // Get the variation product object
                $regular_price = $variation->get_regular_price();
                $sale_price = $variation->get_sale_price();

                if ( $regular_price && $sale_price ) {
                    // Calculate the sale percentage for the variation
                    $percentage = round( ( ( $regular_price - $sale_price ) / $regular_price ) * 100 );
                    $total_percentage += $percentage;
                    $count++;
                }
            }

            // Display the average sale percentage or a dash if no variations are on sale
            echo $count > 0 ? round( $total_percentage / $count ) . '%' : '—';

        } elseif ( $product->is_on_sale() ) {
            // For simple products, calculate and display the sale percentage
            $regular_price = $product->get_regular_price();
            $sale_price = $product->get_sale_price();

            if ( $regular_price && $sale_price ) {
                $percentage = round( ( ( $regular_price - $sale_price ) / $regular_price ) * 100 );
                echo $percentage . '%';
            } else {
                echo '—';
            }
        } else {
            // If the product is not on sale, display a dash
            echo '—';
        }
    }
}
add_action( 'manage_product_posts_custom_column', 'display_sale_percentage_in_column', 10, 2 );

/**
 * Make the Sale Percentage column sortable in the WooCommerce Products admin table.
 *
 * @param array $columns Existing sortable columns.
 * @return array Modified sortable columns with the Sale Percentage column added.
 */
function make_sale_percentage_column_sortable( $columns ) {
    $columns['sale_percentage'] = 'sale_percentage'; // Add the Sale Percentage column as sortable
    return $columns;
}
add_filter( 'manage_edit-product_sortable_columns', 'make_sale_percentage_column_sortable' );
?>