Cart item quantity progressive percentage discount in Woocommerce 3

Question

I am trying to apply a TOTAL CART discount to all the items in the cart, depending on the quantity of items added. I have taken and modified the code example from answer here and got most of the logic working.

I cannot however get it working for two scenarios described below. It also only applies the rule to a single item in the cart. Not the entire cart.

Scenario:

• If no of items in the cart are between 9-12, Apply 5% Discount to all items.
• If no of items in the cart are between 13-16, Apply 10% Discount to all items.
• The discount's should not stack. eg when 12 items in cart, apply 5% discount...when 13 items added, remove 5% discount and apply 10% discount.

Code:

add_filter('woocommerce_add_cart_item_data', 'add_items_default_price_as_custom_data', 20, 3 );
function add_items_default_price_as_custom_data( $cart_item_data, $product_id, $variation_id ){
    $product_id = $variation_id > 0 ? $variation_id : $product_id;

    ## ----- YOUR SETTING ----- ##
    $discount_percentage = 5; // Discount (5%)

    // The WC_Product Object
    $product = wc_get_product($product_id);

    // Only for non on sale products
    if( ! $product->is_on_sale() ){
        $price = (float) $product->get_price();

        // Set the Product default base price as custom cart item data
        $cart_item_data['base_price'] = $price;

        // Set the Product discounted price as custom cart item data
        $cart_item_data['new_price'] = $price * (100 - $discount_percentage) / 100;

        // Set the percentage as custom cart item data
        $cart_item_data['percentage'] = $discount_percentage;
    }

    return $cart_item_data;
}

// Display the product original price
add_filter('woocommerce_cart_item_price', 'display_cart_items_default_price', 20, 3 );
function display_cart_items_default_price( $product_price, $cart_item, $cart_item_key ){
    if( isset($cart_item['base_price']) ) {
        $product        = $cart_item['data'];
        $product_price  = wc_price( wc_get_price_to_display( $product, array( 'price' => $cart_item['base_price'] ) ) );
    }
    return $product_price;
}

// Display the product name with the discount percentage
add_filter( 'woocommerce_cart_item_name', 'append_percetage_to_item_name', 20, 3 );
function append_percetage_to_item_name( $product_name, $cart_item, $cart_item_key ){
    if( isset($cart_item['percentage']) && isset($cart_item['base_price']) ) {
        if( $cart_item['data']->get_price() != $cart_item['base_price'] )
            $product_name .= ' <em>(' . $cart_item['percentage'] . '% discounted)</em>';
    }
    return $product_name;
}

add_action( 'woocommerce_before_calculate_totals', 'custom_discounted_cart_item_price', 20, 1 );
function custom_discounted_cart_item_price( $cart ) {

    ## ----- YOUR SETTING ----- ##
    $balanced_qty = 9; // Targeted quantity
    $upper_balanced_qty = 12; // Max quantity limit
    // Loop through cart items
    foreach ( $cart->get_cart() as $cart_item ) {

        // For item quantity between 9 and 12
        if( ($cart_item['quantity'] >= $balanced_qty && isset($cart_item['new_price']) && ($cart_item['quantity'] <= $upper_balanced_qty) ) ){

            // Set cart item discounted price
            $cart_item['data']->set_price($cart_item['new_price']);
        }
    }
}

Answer 1

You can add a discount to the whole cart by apply a negative fee.

See: Apply a discount on the cart content total excluding taxes in WooCommerce

Try the code below

add_action( 'woocommerce_before_calculate_totals', 'custom_discounted_cart_item_price', 20, 1 );
function custom_discounted_cart_item_price( $cart ) {
  $total_cart_items_count = $cart->get_cart_contents_count();
  $discount = null;

  // Apply 5% discount between 9 - 12 items
  if( $total_cart_items_count >= 9 && $total_cart_items_count <= 12 ) {
    // Calculate 5% of cart total
    $discount = $cart->get_cart_contents_total() * 5 / 100;
  }

  // Apply 10% discount between 13 - 16 items
  if( $total_cart_items_count >= 13 && $total_cart_items_count <= 16 ) {
    // Calculate 10% of cart total
    $discount = $cart->get_cart_contents_total() * 10 / 100;
  }

  if( !empty( $discount ) ) {
    $cart->add_fee(
      __( 'Discount', 'woocommerce' ) . '($percent%)',
      -$discount,
      false // TAX
    );
  }
}

Answer 2

You can do it by cart item quantity or globally based on cart items count:

1) By cart item quantity:

// Utility function that give the discount percentage based on quantity argument
function get_discount_percent( $quantity ){
    if( $quantity < 9 )
        $percent = 0;  // 0 %  ( quantity from 1 to 8 )
    elseif( $quantity >= 9 && $quantity < 13 )
        $percent = 5;  // 5 %  ( quantity from 9 to 12 )
    else
        $percent = 10; // 10 % ( quantity up to 13 )

    return $percent;
}


add_filter('woocommerce_add_cart_item_data', 'add_items_default_price_as_custom_data', 20, 3 );
function add_items_default_price_as_custom_data( $cart_item_data, $product_id, $variation_id ){
    $product_id = $variation_id > 0 ? $variation_id : $product_id;

    ## ----- YOUR SETTING ----- ##
    $percent_1 = 5; //  Discount (5%)
    $percent_2 = 10; // Discount (10%)

    // The WC_Product Object
    $product = wc_get_product($product_id);

    $price = (float) $product->get_price();

    // Set the Product default base price as custom cart item data
    $cart_item_data['discount'][0] = $price;

    // Set the Product discounted price of 5% as custom cart item data
    $cart_item_data['discount'][$percent_1] = $price * (100 - $percent_1) / 100;

    // Set the Product discounted price of 10% as custom cart item data
    $cart_item_data['discount'][$percent_2] = $price * (100 - $percent_2) / 100;

    return $cart_item_data;
}

// Display the product original price
add_filter('woocommerce_cart_item_price', 'display_cart_items_default_price', 20, 3 );
function display_cart_items_default_price( $product_price, $cart_item, $cart_item_key ){
    if( isset($cart_item['discount'][0]) ) {
        $product        = $cart_item['data'];
        $product_price  = wc_price( wc_get_price_to_display( $product, array( 'price' => $cart_item['discount'][0] ) ) );
    }
    return $product_price;
}

// Display the product name with the discount percentage
add_filter( 'woocommerce_cart_item_name', 'append_percetage_to_item_name', 20, 3 );
function append_percetage_to_item_name( $product_name, $cart_item, $cart_item_key ){
    // get the percent based on quantity
    $percent = get_discount_percent($cart_item['quantity']);

    if( isset($cart_item['discount'][$percent]) && isset($cart_item['discount'][0]) ) {
        if( $cart_item['data']->get_price() != $cart_item['discount'][0] )
            $product_name .= ' <em>(' . $percent . '% discounted)</em>';
    }
    return $product_name;
}

add_action( 'woocommerce_before_calculate_totals', 'set_custom_discount_cart_item_price', 25, 1 );
function set_custom_discount_cart_item_price( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    foreach( $cart->get_cart() as $cart_item ){
        // get the percent based on quantity
        $percentage = get_discount_percent($cart_item['quantity']);

        // For items non on sale set a discount based on quantity as defined in
        if( $percentage != 0 && isset($cart_item['discount'][$percentage]) && ! $cart_item['data']->is_on_sale() ) {
            $cart_item['data']->set_price($cart_item['discount'][$percentage]);
        }
    }
}

Code goes in function.php file of your active child theme (or active theme). Tested and works.

---

2) Globally on cart item count (for non on sale products) :

// Utility function that give the discount percentage based on quantity argument
function get_discount_percent( $quantity ){
    if( $quantity < 9 )
        $percent = 0;  // 0 %  ( quantity from 1 to 8 )
    elseif( $quantity >= 9 && $quantity < 13 )
        $percent = 5;  // 5 %  ( quantity from 9 to 12 )
    else
        $percent = 10; // 10 % ( quantity up to 13 )

    return $percent;
}

// Utility function that count cart items that are not on sale
function get_non_on_sale_cart_items_count(){
    $items_count = 0;
    foreach( WC()->cart->get_cart() as $cart_item ){
        if( ! $cart_item['data']->is_on_sale() ){
            $items_count += $cart_item['quantity'];
        }
    }
    return $items_count;
}


add_filter('woocommerce_add_cart_item_data', 'add_items_default_price_as_custom_data', 20, 3 );
function add_items_default_price_as_custom_data( $cart_item_data, $product_id, $variation_id ){
    $product_id = $variation_id > 0 ? $variation_id : $product_id;

    ## ----- YOUR SETTING ----- ##
    $percent_1 = 5; //  Discount (5%)
    $percent_2 = 10; // Discount (10%)

    // The WC_Product Object
    $product = wc_get_product($product_id);

    $price = (float) $product->get_price();

    // Set the Product default base price as custom cart item data
    $cart_item_data['discount'][0] = $price;

    // Set the Product discounted price of 5% as custom cart item data
    $cart_item_data['discount'][$percent_1] = $price * (100 - $percent_1) / 100;

    // Set the Product discounted price of 10% as custom cart item data
    $cart_item_data['discount'][$percent_2] = $price * (100 - $percent_2) / 100;

    return $cart_item_data;
}

// Display the product original price
add_filter('woocommerce_cart_item_price', 'display_cart_items_default_price', 20, 3 );
function display_cart_items_default_price( $product_price, $cart_item, $cart_item_key ){
    if( isset($cart_item['discount'][0]) ) {
        $product        = $cart_item['data'];
        $product_price  = wc_price( wc_get_price_to_display( $product, array( 'price' => $cart_item['discount'][0] ) ) );
    }
    return $product_price;
}

// Display the product name with the discount percentage
add_filter( 'woocommerce_cart_item_name', 'append_percetage_to_item_name', 20, 3 );
function append_percetage_to_item_name( $product_name, $cart_item, $cart_item_key ){
    // Get cart items count
    $items_count = get_non_on_sale_cart_items_count();

    // get the percent based on quantity
    $percent = get_discount_percent($items_count);

    if( isset($cart_item['discount'][$percent]) && isset($cart_item['discount'][0]) ) {
        if( $cart_item['data']->get_price() != $cart_item['discount'][0] )
            $product_name .= ' <em>(' . $percent . '% discounted)</em>';
        elseif ( $cart_item['data']->is_on_sale() && $percent != 0 ){
            $product_name .= ' <em>(Item on sale)</em>';
        }
    }
    return $product_name;
}

// Change cart item price
add_action( 'woocommerce_before_calculate_totals', 'set_custom_discount_cart_item_price', 25, 1 );
function set_custom_discount_cart_item_price( $cart ) {
    if ( is_admin() && ! defined( 'DOING_AJAX' ) )
        return;

    if ( did_action( 'woocommerce_before_calculate_totals' ) >= 2 )
        return;

    // Get cart items count
    $items_count = get_non_on_sale_cart_items_count();

    // get the percent based on quantity
    $percentage = get_discount_percent($items_count);

    foreach( $cart->get_cart() as $cart_item ){
        // For items non on sale set a discount based on quantity as defined in
        if( $percentage != 0 && isset($cart_item['discount'][$percentage]) && ! $cart_item['data']->is_on_sale() ) {
            $cart_item['data']->set_price($cart_item['discount'][$percentage]);
        }
    }
}

Code goes in function.php file of your active child theme (or active theme). Tested and works.

Here below, in this example, the third item is on sale, so the real count is 10 + 1 = 11 items and then the discount for 11 items is 5% :