Apply Cart Discount Based on Quantity

This snippet applies a discount to the cart based on the total quantity of items, encouraging bulk purchases.

PHP

function apply_cart_quantity_discount( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) ) return;

    $total_quantity = $cart->get_cart_contents_count();
    $discount_percentage = 0;

    if ( $total_quantity >= 10 && $total_quantity < 20 ) {
        $discount_percentage = 5;
    } elseif ( $total_quantity >= 20 ) {
        $discount_percentage = 10;
    }

    if ( $discount_percentage > 0 ) {
        $discount = ( $cart->subtotal / 100 ) * $discount_percentage;
        $cart->add_fee( 'Bulk Discount', -$discount );
    }
}
add_action( 'woocommerce_cart_calculate_fees', 'apply_cart_quantity_discount' );