以下代码在加载页面时考虑产品数量，然后在更改产品数量时更新价格。

通过代码中添加的注释标签进行解释

function action_woocommerce_single_product_summary() {
    global $product;
    
    // Getters
    $price = $product->get_price();
    $currency_symbol = get_woocommerce_currency_symbol();
    
    // let's setup our div
    echo sprintf('<div id="product_total_price" style="margin-bottom:20px;">%s %s</div>', __('Product Total:','woocommerce'), '<span class="price">' . $currency_symbol . $price . '</span>' );
    ?>
    <script>
    jQuery(function($) {
        // jQuery variables
        var price = <?php echo $price; ?>, 
            currency = '<?php echo $currency_symbol; ?>',
            quantity =  $( '[name=quantity]' ).val();
            
        // Code to run when the document is ready
        var product_total = parseFloat( price * quantity );
        $( '#product_total_price .price' ).html( currency + product_total.toFixed( 2 ) );
            
        // On change
        $( '[name=quantity]' ).change( function() {
            if ( ! ( this.value < 1 ) ) {
                product_total = parseFloat( price * this.value );

                $( '#product_total_price .price' ).html( currency + product_total.toFixed( 2 ) );
            }
        });
    });
    </script>
    <?php

}
// We are going to hook this on priority 31, so that it would display below add to cart button.
add_action( 'woocommerce_single_product_summary', 'action_woocommerce_single_product_summary', 31, 0 );