GET a coupon code via URL and apply it in WooCommerce Checkout page [closed]

I have a WooCommerce website and when customer add-to-cart a product, it is get redirected to checkout page, so cart page is not accessible.

I would like to apply coupon via URL (GET) on checkout page, with something like https://example.com/?coupon_code=highfive.

When customer click this URL then the coupon code is stored in browser sessions. Then if he add-to-cart any product then the coupon is applied into checkout page.

Is this possible?

Answer

Update 3: This can be done in a very simple way with the following 2 hooked functions:

• The first one will catch the coupon code in the Url and will set it in WC_Sessions.
• The second one will apply the coupon code from session in checkout page.

Here is this code:

add_action('init', 'get_custom_coupon_code_to_session');
function get_custom_coupon_code_to_session(){
    if( isset($_GET['coupon_code']) ){
        // Ensure that customer session is started
        if( isset(WC()->session) && ! WC()->session->has_session() )
            WC()->session->set_customer_session_cookie(true);
            
        // Check and register coupon code in a custom session variable
        $coupon_code = WC()->session->get('coupon_code');
        if(empty($coupon_code)){
            $coupon_code = esc_attr( $_GET['coupon_code'] );
            WC()->session->set( 'coupon_code', $coupon_code ); // Set the coupon code in session
        }
    }
}

add_action( 'woocommerce_before_checkout_form', 'add_discout_to_checkout', 10, 0 );
function add_discout_to_checkout( ) {
    // Set coupon code
    $coupon_code = WC()->session->get('coupon_code');
    if ( ! empty( $coupon_code ) && ! WC()->cart->has_discount( $coupon_code ) ){
        WC()->cart->add_discount( $coupon_code ); // apply the coupon discount
        WC()->session->__unset('coupon_code'); // remove coupon code from session
    }
}

Code goes in function.php file of the active child theme (or active theme). Tested and works

Inspired from this answer code, Lukasz Wiktor has published a plugin: Woo Coupon URL