问只允许在Woocommerce中购买一件物品

EN

// Allowing adding only one unique item to cart and displaying an error message
add_filter( 'woocommerce_add_to_cart_validation', 'add_to_cart_validation', 10, 1 );
function add_to_cart_validation( $passed ) {
    if( ! WC()->cart->is_empty() ){
        wc_add_notice( __("You can add only one item to cart", "woocommerce" ), 'error' );
        $passed = false;
    }
    return $passed;
}

// Avoiding checkout when there is more than one item and displaying an error message
add_action( 'woocommerce_check_cart_items', 'check_cart_items' ); // Cart and Checkout
function check_cart_items() {
    if( sizeof( WC()->cart->get_cart() ) > 1 ){
        // Display an error message
        wc_add_notice( __("More than one items in cart is not allowed to checkout", "woocommece"), 'error' );
    }
}

// Removing on add to cart if an item is already in cart
add_filter( 'woocommerce_add_cart_item_data', 'remove_before_add_to_cart' );
function remove_before_add_to_cart( $cart_item_data ) {
    WC()->cart->empty_cart();
    return $cart_item_data;
}

// Removing one item on cart item check if there is more than 1 item in cart
add_action( 'template_redirect', 'checking_cart_items' ); // Cart and Checkout
function checking_cart_items() {
    if( sizeof( WC()->cart->get_cart() ) > 1 ){
        $cart_items_keys = array_keys(WC()->cart->get_cart());
        WC()->cart->remove_cart_item($cart_items_keys[0]);
    }
}