$replace_order = new WC_Cart();
$replace_order->empty_cart( true );
$replace_order->add_to_cart( \"256\", \"1\");
The above code add product
I have tried all above code samples and latest woocommerce 3.0 is not support any of the above example. Use below code and working perfectly for me.
add_action( 'woocommerce_before_calculate_totals', 'add_custom_price' );
function add_custom_price( $cart_object ) {
$custom_price = 10; // This will be your custom price
foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) {
$cart_item['data']->set_price($custom_price);
}
}