Conditionally displaying a notice about free shipping in Woocommerce

Question

I wrote PHP code to display a Woocommerce notice - "free shipping for $40 & under" only once on shop page and once on cart page, but also in cart should not be more than 40$. The code works, but i am not sure that it is the best way to do it:

$actual_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") . "://$_SERVER[HTTP_HOST]$_SERVER[REQUEST_URI]";

$shop_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") ."://$_SERVER[HTTP_HOST]/shop/";

$cart_link = (isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http") ."://$_SERVER[HTTP_HOST]/cart/";

$first_time_shop = false;

if ((!isset($_COOKIE["mynoticeshop"]))&&($actual_link == $shop_link))
{
    $first_time_shop = true;
    setcookie("mynoticeshop", "mynoticesaleshop", time() + 600, $shop_link);
}
if ($first_time_shop) {
   function sp_custom_notice() {
        $subtotal = WC()->cart->subtotal;
        $free_shipping_threshold = 40;
        if ($subtotal < $free_shipping_threshold) {
        wc_add_notice( 'free shipping for $40 & under', 'notice' );
    }
}

add_filter( 'woocommerce_init', 'sp_custom_notice' );
}

$first_time_cart = false;
if ((!isset($_COOKIE["mynoticecart"]))&&($actual_link == $cart_link)) {
    $first_time_cart = true;
    setcookie("mynoticecart", "mynoticesalecart", time() + 600, $cart_link);
}
if ($first_time_cart) {
   function sp_custom_notice() {
        $subtotal = WC()->cart->subtotal;
        $free_shipping_threshold = 40;
        if ($subtotal < $free_shipping_threshold) {
        wc_add_notice( ' free shipping for $40 & under', 'notice' );
    }
}

add_filter( 'woocommerce_init', 'sp_custom_notice' );
}

I am new to Programming and I am interested to know if there is a better and shorter solution of this code?

Answer 1

Don't Repeat Yourself

The D.R.Y. principle is a fundamental principle in programming. Anytime logic is repeated more than once, it should be abstracted. For example, the first three variable assignments contain the same ternary operation:

(isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http")

That could be put into a function:

function GetProtocol() {
    return isset($_SERVER['HTTPS']) && $_SERVER['HTTPS'] === 'on' ? "https" : "http";
}

That way if any of that logic needed to be updated, it could be changed in once place instead of three. The HTTP_HOST could also be included in that function - in that case, a name of GetProtocolAndDomain would be appropriate.

Like Peter's answer on SO mentions- the function sp_custom_notice() can be declared once, since the only difference between the two definitions appears to be the last line - where the first argument passed is 'free shipping for $40 & under' in the first case and the first argument is ' free shipping for $40 & under' in the second case. There isn't really a need for a space in the second case?

Peter also claims the first three variables are not necessary:

Firstly, you don't need the 3 $*_link variables as WooCommerce has 2 conditionals - is_shop() and is_cart() to check if you're on a shop page or a cart page. Also, the , $shop_link & , $cart_link in the setcookies aren't required, so you can safely get rid of them.¹

This makes sense, since you can have the cookies available for all pages on the domain instead of just a single page. In the event that is_shop() and is_cart() weren't available, you could compare the last 5 characters of $_SERVER[REQUEST_URI] with cart/ or shop/ using substr() with -5 as the start parameter.

Threshold constant

It appears that the value for $free_shipping_threshold doesn't change. Because of this, it can be made a constant at the top of the file:

const FREE_SHIPPING_CONSTANT = 40;

Then that constant can be used in the sp_custom_notice function, and if that value needed to be updated, you could just look at the top of the file for the line to change.

Erroneous Line

I see the following line in your post:

$first_time_shop = true;<br>

Did you manually add the HTML break tag (i.e. <br>) when posting here? I would expect that if that was actually in your code then the PHP interpreter would thrown an error.