php - Minimum weight and mandatory product categories requirements in WooCommerce

Solution:

The following will enable a minimum weight for "Formaggi" category (Cheese) and avoid to buy items from "Coltelli" category (knives) without items from "Formaggi" category (Cheese):

add_action( 'woocommerce_check_cart_items', 'minimum_weight_and_category_requirements' );
function minimum_weight_and_category_requirements() {
    // Only on cart and check out pages
    if( ! ( is_cart() || is_checkout() ) ) return;
    
    // Your settings:
    $min_weight = 0.750; // Minimum weight( 750 GR )
    $formaggi   = array('Formaggi'); // The category for weight calculation
    $coltelli   = array('Coltelli'); // The category that requires 'Formaggi'
    
    // Initializing
    $total_weight   = 0; 
    $coltelli_found = $remove_button = false;

    // Loop through cart items        
    foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {  
        // Has weight and 'Formaggi' category
        if ( $cart_item['data']->get_weight() > 0 && has_term( $formaggi, 'product_cat', $cart_item['product_id'] ) ) {
            // Add to total weight
            $total_weight += $cart_item['quantity'] * $cart_item['data']->get_weight();
        }

        // Has 'coltelli' category
        if ( has_term( $coltelli, 'product_cat', $cart_item['product_id'] ) ) {
            $coltelli_found = true; // Found 'coltelli'
        }
    }

    // When total weight is less than the minimum require weight for "Formaggi" category
    if( $total_weight > 0 && $total_weight < $min_weight ) {
        // Displays a dynamic error notice
        wc_add_notice( sprintf( '<strong>%s</strong> <br>%s: %s',
            __("Per i Formaggi ГЁ richiesto un acquisto minimo di 750 gr."),
            __("Peso dei Formaggi nel carrello"),
            wc_format_weight($total_weight)
        ), 'error' );
        
        $remove_button = true;
    }
    
    // When "Coltelli" category is purchased without "Formaggi" category
    if( $total_weight == 0 && $coltelli_found ) {
        // Displays a dynamic error notice
        wc_add_notice( sprintf( __("Gli articoli %s possono essere acquistati solo con un ordine di %s."),
            '<strong>"' . __("Coltelli") . '"</strong>',
            '<strong>"' . __("Formaggi") . '"</strong>'
        ), 'error' );
        
        $remove_button = true;
    }
    
    // Remove "Proceed to checkout" button
    if( $remove_button ) {
        remove_action( 'woocommerce_proceed_to_checkout','woocommerce_button_proceed_to_checkout', 20);
    }
}
Copy code

Code goes on functions.php file of your active child theme (or active theme). It should works.

Related: Minimum cart amount for specific product categories in WooCommerce