php - Minimum cart item quantity for specific product categories in WooCommerce

Question

In WooCommerce, I need to set up a minimum quantity for each item of a product category. I searched the forum and found some code that works fine except it only counts the Quantity for a product category in total:

add_action( 'woocommerce_checkout_process', 'wc_minimum_order_amount' );
add_action( 'woocommerce_before_cart' , 'wc_minimum_order_amount' );
function wc_minimum_order_amount() {
    $minimum = 5; //Qty product

    if ( WC()->cart->cart_contents_count < $minimum ) {
        $draught_links = array();

        foreach(WC()->cart->get_cart() as $cart_item_key => $values ) {
            $_product = $values['data'];

            $terms = get_the_terms( $_product->id, 'product_cat' );

            foreach ($terms as $term) {
                $draught_links[] = $term->name;
            }   
        }

        if (in_array("Noten", $draught_links)){
            $on_draught = true;
        }else{
            $on_draught = false;
        }

        if( is_cart() ) {
            if($on_draught){
                wc_print_notice( 
                    sprintf( 'Bitte beachte die Mindestbestellmenge. Du brauchst mindestens %s Notenexemplare pro Arrangement. Aktuell hast du %s Stück in deinem Warenkorb.' , 
                         $minimum , 
                         WC()->cart->cart_contents_count
                    ), 'error' 
                );
            }
        } else {
            if($on_draught){
                wc_add_notice( 
                    sprintf( 'Bitte beachte die Mindestbestellmenge. Du brauchst mindestens %s Notenexemplare pro Arrangement. Aktuell hast du %s Stück in deinem Warenkorb.' , 
                        $minimum , 
                        WC()->cart->cart_contents_count
                    ), 'error' 
                );
            }
        }
    }
}

For example if I have two products (A and B) of belonging to the same product category and set up minimum quantity for this category to 5, the error message for the customer won't appear in this case:

• Product A: 3
• Product B: 2

I need a min quantity of 5 for every single product of that category.

Do you have an idea how to change and optimize the following code?

Answer 1

Since WooCommerce 3, your actual code is outdated and not convenient… There is multiple ways:

1). The best way: Set up the minimum quantity at product level (for a product category):

// On single product pages
add_filter( 'woocommerce_quantity_input_args', 'min_qty_filter_callback', 20, 2 );
function min_qty_filter_callback( $args, $product ) {
    $categories = array('Noten'); // The targeted product category(ies)
    $min_qty    = 5; // The minimum product quantity

    $product_id = $product->is_type('variation') ? $product->get_parent_id() : $product->get_id();

    if( has_term( $categories, 'product_cat', $product_id ) ){
        $args['min_value'] = $min_qty;
    }
    return $args;
}

// On shop and archives pages
add_filter( 'woocommerce_loop_add_to_cart_args', 'min_qty_loop_add_to_cart_args', 10, 2 );
function min_qty_loop_add_to_cart_args( $args, $product ) {
    $categories = array('Noten'); // The targeted product category
    $min_qty    = 5; // The minimum product quantity

    $product_id = $product->get_id();

    if( has_term( $categories, 'product_cat', $product_id ) ){
        $args['quantity'] = $min_qty;
    }
    return $args;
}

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

2). Alternative way: Checking cart items and displaying an error message (similar to your code):

add_action( 'woocommerce_check_cart_items', 'wc_min_item_required_qty' );
function wc_min_item_required_qty() {
    $categories    = array('Noten'); // The targeted product category
    $min_item_qty  = 5; // Minimum Qty required (for each item)
    $display_error = false; // Initializing

    // Loop through cart items
    foreach(WC()->cart->get_cart() as $cart_item ) {
        $item_quantity = $cart_item['quantity']; // Cart item quantity
        $product_id    = $cart_item['product_id']; // The product ID

        // For cart items remaining to "Noten" producct category
        if( has_term( $categories, 'product_cat', $product_id ) && $item_quantity < $min_item_qty ) {
            wc_clear_notices(); // Clear all other notices

            // Add an error notice (and avoid checkout).
            wc_add_notice( sprintf( 'Bitte beachte die Mindestbestellmenge. Du brauchst mindestens %s Notenexemplare pro Arrangement. Aktuell hast du %s Stück in deinem Warenkorb.', $min_item_qty , $item_quantity ), 'error' );
            break; // Stop the loop
        }
    }
}

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

---

To make it work for parent product category too, you will also add this custom function:

// Custom conditional function that handle parent product categories too
function has_product_categories( $categories, $product_id = 0 ) {
    $parent_term_ids = $categories_ids = array(); // Initializing
    $taxonomy        = 'product_cat';
    $product_id      = $product_id == 0 ? get_the_id() : $product_id;

    if( is_string( $categories ) ) {
        $categories = (array) $categories; // Convert string to array
    }

    // Convert categories term names and slugs to categories term ids
    foreach ( $categories as $category ){
        $result = (array) term_exists( $category, $taxonomy );
        if ( ! empty( $result ) ) {
            $categories_ids[] = reset($result);
        }
    }

    // Loop through the current product category terms to get only parent main category term
    foreach( get_the_terms( $product_id, $taxonomy ) as $term ){
        if( $term->parent > 0 ){
            $parent_term_ids[] = $term->parent; // Set the parent product category
            $parent_term_ids[] = $term->term_id; // (and the child)
        } else {
            $parent_term_ids[] = $term->term_id; // It is the Main category term and we set it.
        }
    }
    return array_intersect( $categories_ids, array_unique($parent_term_ids) ) ? true : false;
}

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

Then in the existing code, you will replace:

has_term( $category, 'product_cat', $product_id )

by

has_product_categories( $category, $product_id )

That will allow you to handle parent product categories too.