Woocommerce Add a product to the cart programmatically

/**
* @Title: Woocommerce Add a product to the cart programmatically
* @Author: Mina Pansuriya
* @Website: http://minapansuriya.com
* @Blog URL: http://minapansuriya.com/woocommerce-add-a-product-to-the-cart-programmatically/
*/
add_action( 'template_redirect', 'pbs_woo_add_gift_product_to_the_cart' );
function pbs_woo_add_gift_product_to_the_cart() {
    $isAddGiftF = false;
    
    if( is_cart() || is_checkout() ) 
    {
        foreach ( WC()->cart->get_cart() as $cart_item_key => $cart_item ) 
        {
             $product = $cart_item['data'];
            // If Product is THE product, add free gift
            if($product->id == "331")
            {
                $isAddGiftF = true;
            }
            else if($product->id == "15722")
            {
                // If gift is already exist in the cart, don't add it again
                $isAddGiftF = false;
            }
        }
        
        if($isAddGiftF)
        {
            // Here First Parameter is Product Id and second partmeter is no. of products
            WC()->cart->add_to_cart( 15722, 1 );
        }
    }
}