Limit the number of cart Items in Woocommerce

There is 2 actions to check and to control if you want to limit cart items:

1. Add to basket - When product  is added to cart
2. Update Basket - When quantities are updated in cart page

Add a custom function hooked in woocommerce_add_to_cart_validation filter hook in function.php file of your active child theme (or theme), will allow customer to restrict the cart items to 'n' max and to display a custom message when this limit is exceeded:

1. Checking and validating when products are added to cart:
• Restrict Total Transaction Items:
  add_filter( 'woocommerce_add_to_cart_validation', 'only_n_items_allowed_add_to_cart', 10, 3 );
function only_n_items_allowed_add_to_cart( $passed, $product_id, $quantity ) {
$cart_items_count = WC()->cart->get_cart_contents_count();
$total_count = $cart_items_count + $quantity;

if( $cart_items_count >= n || $total_count > n ){
// Set to false
$passed = false;
// Display a message
wc_add_notice( __( "You can’t have more than n items in cart", "woocommerce" ), "error" );
}
return $passed;
}
• Restrict Item in a transaction:
  add_filter( 'woocommerce_add_to_cart_validation', 'only_five_items_allowed_add_to_cart', 10, 3 );
function only_five_items_allowed_add_to_cart( $passed, $product_id, $quantity ) {

//$cart_items_count = WC()->cart->get_cart_contents_count();

foreach ( WC()->cart->get_cart() as $cart_item ) {
if($cart_item['product_id'] == $product_id ){
$cart_items_count = $cart_item['quantity'];
break; // stop the loop if product is found
}
}

$total_count = $cart_items_count + $quantity;

if( $cart_items_count > 3 || $total_count > 3 ){
// Set to false
$passed = false;
// Display a message
wc_add_notice( __( "You can’t add more than 3 items in cart", "woocommerce" ), "error" );
}
return $passed;
}


2. Checking and validating when updating cart item quantities when products are added to cart

• Restrict Total Transaction Items:
  add_filter( 'woocommerce_update_cart_validation', 'only_six_items_allowed_cart_update', 10, 4 );
function only_six_items_allowed_cart_update( $passed, $cart_item_key, $values, $updated_quantity ) {

$cart_items_count = WC()->cart->get_cart_contents_count();
$original_quantity = $values['quantity'];
$total_count = $cart_items_count - $original_quantity + $updated_quantity;

if( $cart_items_count > 6 || $total_count > 6 ){
// Set to false
$passed = false;
// Display a message
wc_add_notice( __( "You can’t have more than 6 items in cart", "woocommerce" ), "error" );
}
return $passed;
}

• Restrict Item in a transaction:
  add_filter( 'woocommerce_update_cart_validation', 'only_five_items_allowed_cart_update', 10, 4 );
function only_five_items_allowed_cart_update( $passed, $cart_item_key, $values, $updated_quantity ) {

$cart_items_count = WC()->cart->get_cart_contents_count();
$original_quantity = $values['quantity'];
$total_count = $cart_items_count - $original_quantity + $updated_quantity;

if( $updated_quantity > 3 ){
// Set to false
$passed = false;
// Display a message
wc_add_notice( __( "You can’t have more than 3 items in cart", "woocommerce" ), "error" );
}
return $passed;
}