Discount based on WooCommerce product custom input fields

Question

I'm trying to give the user a discount based on a quantity field in the single product page.

Basically, the website sells tickets and I have a different price for adults and for children. So I created input fields in the single product page so the user would type how many adults and how many children he is buying for.

In the product admin I have a ACF (advanced custom field) for "children discount", so in the cart I want to give this discount based on the amount of children. For example, let's say that for this product the user is buying 5 tickets, 3 for adults and 2 for children, I want to calculate a discount for these 2 children.

What I've tried so far:

add_action( 'woocommerce_before_add_to_cart_button', 'custom_product_price_field', 5 );

function custom_product_price_field(){

    echo '<div class="custom-text text">
              <p>Quantity of adults:</p>
              <input type="text" name="qtty_adults" value="" title="Quantity Adults" class="qtty-field">
          </div>
          <div class="custom-text text">
              <p>Quantity of children:</p>
              <input type="text" name="qtty_kids" value="" title="Quantity Kids" class="qtty-field">
          </div>';

}


add_action('woocommerce_cart_calculate_fees' , 'add_user_discounts');

function add_user_discounts( WC_Cart $cart ){

    global $product;

    $qtty_kids = (float) sanitize_text_field( $_POST['qtty_kids'] );
    $discount_per_kid = (float) get_field('children_discount', $product->id);


    $discount = $qtty_kids * $discount_per_kid;

    $cart->add_fee( 'Discount for children', -$discount);
}

Doing this the discount is always $0

Can anyone give me some help on how to make this happen?

LoicTheAztec · Accepted Answer · 2020-03-02T18:53:35.373

Your code is a bit outdated, with some mistakes and there is a lot of missing things to get what you expect…

Try the following instead (updated):

add_action( 'woocommerce_before_add_to_cart_button', 'custom_product_price_field', 5 );
function custom_product_price_field(){

    echo '<div class="custom-text text">
        <p>'.__("Quantity of adults:").'</p>
        <input type="text" name="qtty_adults" value="" title="'.__("Quantity Adults").'" class="qtty-field">
    </div>
    <div class="custom-text text">
        <p>'.__("Quantity of children:").'</p>
        <input type="text" name="qtty_kids" value="" title="'.__("Quantity Kids").'" class="qtty-field">
    </div>';
}

// Add selected add-on option as custom cart item data
add_filter( 'woocommerce_add_cart_item_data', 'filter_add_cart_item_data_callback', 10, 3 );
function filter_add_cart_item_data_callback( $cart_item_data, $product_id, $variation_id ) {
    if ( isset( $_POST['qtty_kids'] )  && $children_discount = get_field( 'children_discount', $product_id ) ) {
        $cart_item_data['children_discount'] = (float) $children_discount - (float) sanitize_text_field( $_POST['qtty_kids'] );
        $cart_item_data['unique_key']        = md5( microtime().rand() ); // Make each item unique
    }
    return $cart_item_data;
}

// Set a discount based a product custom field(s)
add_action('woocommerce_cart_calculate_fees' , 'add_children_discount', 10, 1 );
function add_children_discount( $cart ){
    if ( is_admin() && ! defined('DOING_AJAX') )
        return;

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

    $discount = 0; // Initialising

    // Loop through cart items
    foreach ( $cart->get_cart() as $cart_item ) {
        if( isset( $cart_item['children_discount'] ) ) {
            $discount += $cart_item['children_discount'];
        }
    }

    if ( $discount > 0 )
        $cart->add_fee( __("Discount for children", "woocommerce"), -$discount );
}

Tested and works.

Thank you so much for helping me on this, I've been struggling for a few days now. I tried your code but I'm getting an error when I add the product to cart: Fatal error: Uncaught Error: Call to a member function get_id() on null in ..../php/functional.php(103) : eval()'d code:770 Stack trace: #0 ..../wp-includes/class-wp-hook.php(290): filter_add_cart_item_data_callback(Array, 82, 0) #1 .../wp-includes/plugin.php(206): WP_Hook->apply_filters(Array, Array) #2 ....... Any idea what could be causing this? — Aldo Constenla Bravo, Mar 02 '20 at 18:34
@A Just updated the code now sorry, a little oversight *(as I haven't try it with the `get_field()` part - ACF field)*… Thank you. — LoicTheAztec, Mar 02 '20 at 18:50
Thank you so much, it worked just fine! Again, I've been searching for a few days and finally someone could really help me on that, you are awesome. Can you give me some directions on where can I learn more about programming like so? I'm more of a front-end guy and I'm starting now with php and such backend programming. Thanks again, you really saved the day — Aldo Constenla Bravo, Mar 02 '20 at 18:55
@AldoConstenlaBravo Welcome… You can learn step by step here in StackOverFlow, trying to answer to some interesting questions real cases and looking to other good answers… Also always keep in your bookmarks [this](https://docs.woocommerce.com/wc-apidocs/hook-docs.html) and don't hesitate to inspect the plugin core files code... — LoicTheAztec, Mar 02 '20 at 19:05

Discount based on WooCommerce product custom input fields

1 Answers1