How to apply quantity discounts to certain products according to the user role?

Question

I need to make discounts to certain user roles of some products, when a certain number of this product is purchased.

The discount should only be applied to the number of products that we have chosen in:

Between 1 and 9 products: no discount.

Product 10: 5% discount on 10 products.

Between 11 & 19 products: 5% discount on first 10 products, no discount for product 11 to 19

20 products: 5% discount on 20 products.

Between 21 & 29 products: 5% discount on first 20 products, no discount for product 21 to 29

30 products : 5% discount on 30 products.

and so on always in batches of 10 (10, 20, 30, 40, ..multiples of 10)

For example: User buys 14 televisions, at a price of €19.00, a 5% discount will be applied to the first 10 units, the remaining 4 do not receive the discount.

---

I EDIT THE QUESTION

With the help of user @yash's answer, I've managed to get what I'm looking for working somewhat.

Only one type of discount can be applied and to specific products.

As I need to make several types of discounts (buy 10 products and get 5% discount - buy 15 products and get 7% discount - buy 12 products and get 4% discount)

I've tried to clone the function in this answer by changing the name and discount data, but I can't get it to work.

How can I do to achieve this?

I have some other option that always displays a text for the discount, but I can't get the echo discount to save. I want to say that , when I go up from 10 products, the discount disappears until I add more products until I reach 20 products, that the discount corresponding to that amount is added, but in between products from 10 to 20, the discount disappears 5% made to the first 10 products

The discount already obtained must be maintained if we increase the products until we reach the next number that is a multiple of 10, which we would add another 5%. I cannot find the correct form. This next function manages to keep the text in the checkout, but when we have quantities of products that are between 10 and 20, are between 20 and 30, are between 30 and 40, etc., the text is set to zero, without saving the discount already obtained

It's the closest we've come to achieving the goal.

See what I'm doing wrong:

function apply_discount_for_quantity($cart)
{
  if (is_admin()) return;
  global $woocommerce;
  $user = wp_get_current_user();
  $user_roles = $user->roles;
  $discount_products = array(383, 411, 412); // productos elegibles para descuento
  $discount_role = 'wholesale_customer'; // rol de usuario elegible para descuento
  $subtotal = $woocommerce->cart->cart_contents_total;
  $count = $woocommerce->cart->cart_contents_count;
  $discount_percent = 0;
  $eligible_products_count = 0; // variable para contar la cantidad de productos elegibles para descuento
  $discount_applied = 0; // variable para guardar el descuento aplicado

  // cycle through the products in the cart to count thecantidad de productos elegibles
  foreach ($cart->cart_contents as $product) {
    if (in_array($product['product_id'], $discount_products)) {
      $eligible_products_count += $product['quantity'];
    }
  }

  if (in_array($discount_role, $user_roles) && $eligible_products_count > 0) {
    // Change the conditions to apply the discount only in multiples of 10
    if ($eligible_products_count % 10 == 0) {
      $discount_percent = 5;
    }
  }

  // Save the applied discount in a variable
  $discount_applied = $subtotal * ($discount_percent / 100);

  // Add the discount to the cart to always show it, even if it does not apply to quantities that are not multiples of 10
  $cart->add_fee('Descuento por cantidad', -$discount_applied);

  //Apply the discount if necessaryo
  if ($discount_percent > 0) {
    $cart->add_fee('Descuento por cantidad', -$discount_applied);
  }
}
add_action('woocommerce_cart_calculate_fees', 'apply_discount_for_quantity');

Answer 1

New answer

I am not removing old answer , so you can compare and understand changes

<?php
/**
 * Applies discounts to specific products in the cart based on quantity and user role.
 *
 * @param WC_Cart $cart The cart object to apply discounts to.
 */
function apply_discount_for_quantity($cart)
{
    // Check if user is an administrator and exit early if true
    if (is_admin()) {
        return;
    }

    // Get the current user's role
    $current_user = wp_get_current_user();
    $user_roles = $current_user->roles;
    
    // Set the user role that is eligible for discounts
    $discount_role = 'wholesale_customer';

    // Product IDs of that has discount on bunch of 9 products
    $discount_products_of_9 = array(383, 411, 412);
    $discount_percentage_for_9 = 4; // change here for discount percentage

    // Product IDs of that has discount on bunch of 10 products
    $discount_products_of_10  = array(384, 421, 422);
    $discount_percentage_for_10 = 5; // change here for discount percentage

    // Product IDs of that has discount on bunch of 12 products
    $discount_products_of_12 = array(385, 432, 432);
    $discount_percentage_for_12 = 6; // change here for discount percentage
    
    // Initialize arrays to hold eligible product data for each discount category
    $eligible_products_data_of_9 = $eligible_products_data_of_10 = $eligible_products_data_of_12 = array();

    $total_discount_amount = 0;
    
    // Loop through cart items to find eligible products
    foreach ($cart->cart_contents as $item) {
        
        if (in_array($item["product_id"], $discount_products_of_9 )) {
            // Calculate eligible quantity and price for discount
            $eligible_products_data_of_9[$item["product_id"]]["price"] = $item[ "data" ]->get_price();
            $eligible_products_data_of_9[$item["product_id"]]["qty"] = $item["quantity"] - ($item["quantity"] % 9); // change 9 with different number you want
        }

        if (in_array($item["product_id"], $discount_products_of_10 )) {
            // Calculate eligible quantity and price for discount
            $eligible_products_data_of_10[$item["product_id"]]["price"] = $item[ "data" ]->get_price();
            $eligible_products_data_of_10[$item["product_id"]]["qty"] = $item["quantity"] - ($item["quantity"] % 10); // change 10 with different number you want
        }

        if (in_array($item["product_id"], $discount_products_of_12 )) {
            // Calculate eligible quantity and price for discount
            $eligible_products_data_of_12[$item["product_id"]]["price"] = $item[ "data" ]->get_price();
            $eligible_products_data_of_12[$item["product_id"]]["qty"] = $item["quantity"] - ($item["quantity"] % 12); // change 12 with different number you want
        }
    }

    // Apply discount if user is eligible and there are eligible products for each discount category
    if (  in_array($discount_role, $user_roles ) && !empty($eligible_products_data_of_9) ) {
        foreach ($eligible_products_data_of_9 as $eligible_product) {
            $total_discount_amount += ($eligible_product["qty"] * $eligible_product["price"] * $discount_percentage_for_9) / 100;
        }
    }
    if (  in_array($discount_role, $user_roles ) && !empty($eligible_products_data_of_10) ) {
        foreach ($eligible_products_data_of_10 as $eligible_product) {
            $total_discount_amount += ($eligible_product["qty"] * $eligible_product["price"] * $discount_percentage_for_10) / 100;
        }
    }
    if (  in_array($discount_role, $user_roles ) && !empty($eligible_products_data_of_12) ) {
        foreach ($eligible_products_data_of_12 as $eligible_product) {
            $total_discount_amount += ($eligible_product["qty"] * $eligible_product["price"] * $discount_percentage_for_12) / 100;
        }
    }

    // Add discount fee to the cart
    $cart->add_fee("Descuento por cantidad", -$total_discount_amount);
}

// Hook the function to apply the discount on cart calculation
add_action( "woocommerce_cart_calculate_fees",  "apply_discount_for_quantity" );

change in product count and discount percentage as per your requerements

I try to make code more understandable , but let me know for any help or any bug/error .

This answer gives final one discount count but has multiple different calculation OR you want different discounts with separate calculation , In both way total sill remains same, only difference is how you show discount to user , if you want second (separate) way then you divide this into different parts that may help & i'm not very strong at testing so bear with me XD :)

---

---

Old answer

<?php
/**
 * Applies discount based on the quantity of eligible products in the cart
 *  @param object $cart Cart object
 */
function apply_discount_for_quantity($cart)
{
    if (is_admin()) {
        return;
    }

    $current_user = wp_get_current_user();
    $user_roles = $current_user->roles;

    $discount_products = array(383, 411, 412);
    $discount_role = 'wholesale_customer';
    $discount_percentage = 5;
    $total_discount_amount = 0;
    $eligible_products_data = array();

    // Loop through cart items to find eligible products
    foreach ($cart->cart_contents as $item) {
        if (in_array($item["product_id"], $discount_products )) {
            $eligible_products_data[$item["product_id"]]["price"] = $item[ "data" ]->get_price();
            $eligible_products_data[$item["product_id"]]["qty"] = $item["quantity"] - ($item["quantity"] % 10);
        }
    }

    // Apply discount if user is eligible
    if (  in_array($discount_role, $user_roles ) && !empty($eligible_products_data) ) {
        foreach ($eligible_products_data as $eligible_product) {
            $total_discount_amount += ($eligible_product["qty"] * $eligible_product["price"] * $discount_percentage) / 100;
        }
    }

    // Add discount fee to the cart
    $cart->add_fee("Descuento por cantidad", -$total_discount_amount);
}

// Hook the function to apply the discount on cart calculation
add_action( "woocommerce_cart_calculate_fees",  "apply_discount_for_quantity" );

This are test result of my answer for discount(5%) on different quantity :

• quantity is bellow 10
• quantity is 10
• quantity is more then 10 and bellow 20
• quantity is 20
• quantity is more then 20 and bellow 30
• quantity is bellow 30

Answer 2

This is the way I would go about this problem:

1. Gather the numbers of items to be discounted
2. Integer divide the total number of items by $required_quantity
3. Take and multiply that number by recalculated value of the discount for each set of required quantity.

I would also determine if they were a subscriber before passing the cart to the apply_discount function.

A simple version of this would be:

function apply_discount($cart): float {
    $required_quantity = 11; 
    // for this case I am going to assume €19.00 each at 4% discount.
    $block_discount = 19 * 11 * 0.04;
                
    foreach( $cart->get_cart() as $cart_item ){
        $discount = 0
        if(in_array( $cart_item['product_id'], $product_ids )) {
            $discount = $block_discount * intdiv($cart_item['quantity']), $required_quantity);
        }
        if($discount > 0 ){
            $cart->add_fee( 'Discount', -$discount, true, 'standard' );
        }
    }    
}

As for the €88 discount that is roughly 10x what it should be. My guess is $discount = $cart_item['quantity'] * 10;

Answer 3

As I can see in your last exemple

First you can break the logic earlier for

if (!in_array($discount_role, $user_roles)) { return ;}

As you will not apply discount for them

Then you do :

if ($eligible_products_count % 10 == 0) {
      $discount_percent = 5;
    }

If you have 31 eligible products you will got 1 == 0 // false and your discount percent will not change and stay to 0

In your code, only some product can be eligible to trigger the discount, it's look like you will apply the discount to the not eligible product. You should put some of then in your test cart.

So look like to apply more than one discount like Meechew do.

Here my try :

function apply_discount_for_quantity($cart)
        {
            // For sample, I let you choose of to define the rules and send it here
            $discount_rules = [
                ['eligible_product_ids' => [383, 411], 'required_count' => 12, 'discount_percent' => 4],
                ['eligible_product_ids' => [412], 'required_count' => 10, 'discount_percent' => 5],
            ];
            
            $user = wp_get_current_user();
            $user_roles = $user->roles;
            $discount_role = 'wholesale_customer'; // rol de usuario elegible para descuento

            if (!in_array($discount_role, $user_roles)) {
                return;
            }
            
            // Will use counter per lligible product
            $discounts_counter_cache = [];
            
            // cycle through the products in the cart to count thecantidad de productos elegibles
            foreach ($cart->cart_contents as $product) {
                
                //You can put this one on another function to make it more readble)
                foreach ($discount_rules as $rule) {
                    // if product is eligible to one of our discount rule
                    if (in_array($product['product_id'], $rule['eligible_product_ids'])) {

                        // let's count of many product whe got 
                        $discounts_counter_cache[ $product['product_id'] ] = ($discounts_counter_cache[ $product['product_id'] ] ?? 0) + 1;

                        // Apply per elligible product only when it's reach the limit
                        if ($discounts_counter_cache[ $product['product_id'] ] == $rule['required_count']) {
                            // We trigger the discount 
                            $cart->add_fee(
                                'Descuento por cantidad: ' . $rule['discount_percent'] .'% por '. $rule['required_count'] .'x'. $product['product_id'],
                                // You can also set the value in the rule 
                                -($product['product_price'] * $rule['required_count'] * ($rule['discount_percent'] / 100))
                            );
                            
                            // Reset counter
                            $discounts_counter_cache[ $product['product_id'] ] = 0;
                        }
                    }
                }
            }
        }

hope it will help you to found what's you need

Here sample test (test it: https://3v4l.org/ot8A5h):

<?php

class Cart 
{
    protected array $cart = [];
    protected array $fees = [];
    
    public function __construct()
    {
        // generate test Cart
        $testProducts = [
            ['id' => 1 , 'nb' => 22, 'price' => 23],
            ['id' => 383 , 'nb' => 38, 'price' => 19],
            ['id' => 412, 'nb' => 11, 'price' => 34],
        ];
        foreach ($testProducts as $testProduct) {
            while ($testProduct['nb']-- > 0) {
                $this->addProduct($testProduct['id'], $testProduct['price']);
            }
        }
    }
    
    public function cart_contents(): array
    {
        return $this->cart;
    }
    
    public function addProduct(int $id, int $price)
    {
        $this->cart[] = ['product_id' => $id, 'price' => $price];
    }
    
    public function add_fee(string $txt, float $price)
    {
        $this->fees[] = ['txt' => $txt, 'price' => $price];
    }
    
    function apply_discount_for_quantity()
    {
            // For sample, I let you choose of to define the rules and send it here
            $discount_rules = [
                ['eligible_product_ids' => [383, 411], 'required_count' => 12, 'discount_percent' => 4],
                ['eligible_product_ids' => [412], 'required_count' => 10, 'discount_percent' => 5],
            ];
            
            // Will use counter per lligible product
            $discounts_counter_cache = [];
            
            // cycle through the products in the cart to count thecantidad de productos elegibles
            foreach ($this->cart_contents() as $product) {
                
                foreach ($discount_rules as $rule) {
                    // if product is eligible to one of our discount rule
                    if (!in_array($product['product_id'], $rule['eligible_product_ids'])) {
                        // product not eligible for a discount
                        continue;
                    }

                    // let's count of many product whe got 
                    $discounts_counter_cache[ $product['product_id'] ] = ($discounts_counter_cache[ $product['product_id'] ] ?? 0) + 1;

                    // Apply per elligible product only when it's reach the limit
                    if ($discounts_counter_cache[ $product['product_id'] ] == $rule['required_count']) {
                        echo sprintf(' -- Found discount of %d%% to apply on the batch of %d product (id %d) in the cart' . PHP_EOL,
                            $rule['discount_percent'],
                            $rule['required_count'],
                            $product['product_id']
                        );
                        // We trigger the discount 
                        $this->add_fee(
                            'Descuento por cantidad: ' . $rule['discount_percent'] .'% por '. $rule['required_count'] .'x'. $product['product_id'],
                            // You can also set the value in the rule 
                            -($product['price'] * $rule['required_count'] * ($rule['discount_percent'] / 100))
                        );
                        
                        // Reset counter
                        $discounts_counter_cache[ $product['product_id'] ] = 0;
                    }
                    
                }
            }
            
        }
    
    public function show_cart()
    {
        
        $products = [];
        foreach ($this->cart as $entry) {
            if (!isset($products[$entry['product_id']])) {
                $products[$entry['product_id']] = [
                    'id' => $entry['product_id'],
                    'nb' => 0,
                    'price' => $entry['price'],
                    'total' => $entry['price'],
                ];
            }
            $products[$entry['product_id']]['nb']++;
            $products[$entry['product_id']]['price'] += $entry['price'];
        }
        echo 'Cart:'. PHP_EOL;
        foreach ($products as $product) {
            echo sprintf(
                '> Product Id:"%d" - %d$ x %d = %d$'.PHP_EOL,
                $product['id'],
                $product['price'],
                $product['nb'],
                $product['total']
            );
           
        }
        echo PHP_EOL;
        if (!empty($this->fees)) {
            echo 'Fees:'.PHP_EOL;
            $totalFees = ['nb' => 0, 'total' => 0];
            foreach ($this->fees as $fee) {
                $totalFees['nb']++;
                $totalFees['total']+= $fee['price'];
                echo sprintf(
                 '> %d$ - %s' . PHP_EOL,
                 $fee['price'],
                 $fee['txt']
                );
            }
            echo sprintf(
                 '>> Total of %d discounts for %d$' . PHP_EOL,
                 $totalFees['nb'],
                 $totalFees['total']
                );
        }
        
    }
            
}
        
        
 $cart = new Cart();
 echo 'Before discount:'.PHP_EOL;
 echo $cart->show_cart();
 $cart->apply_discount_for_quantity();
 echo PHP_EOL.'After discount:'.PHP_EOL;
 echo $cart->show_cart();

Result:

Before discount: Cart:

Product Id:"1" - 529$ x 22 = 23$ Product Id:"383" - 741$ x 38 = 19$ Product Id:"412" - 408$ x 11 = 34$

-- Found discount of 4% to apply on the batch of 12 product (id 383) in the cart -- Found discount of 4% to apply on the batch of 12 product (id 383) in the cart -- Found discount of 4% to apply on the batch of 12 product (id 383) in the cart -- Found discount of 5% to apply on the batch of 10 product (id 412) in the cart

After discount: Cart:

Product Id:"1" - 529$ x 22 = 23$ Product Id:"383" - 741$ x 38 = 19$ Product Id:"412" - 408$ x 11 = 34$

Fees:

-9$ - Descuento por cantidad: 4% por 12x383 -9$ - Descuento por cantidad: 4% por 12x383 -9$ - Descuento por cantidad: 4% por 12x383 -17$ - Descuento por cantidad: 5% por 10x412

Total of 4 discounts for -44$