Easy WooCommerce global store discounts

functions.php

<?php

//We will use this function to modify prices whenever WooCommerce retrieves them
function mytheme_global_sale_price( $price, $product ) {

    $product_id = $product->get_id();

    //do any checks you need to exclude or include products here
    $excluded_products = [123,678];
    if(in_array($product_id, $excluded_products)) return $price;

    //I am using a custom field to provide an on/off toggle for the global discount, and another for the percentage discount. You could alternatively just hard-code these.
    $global_discount_enabled = get_field('enable_global_discount','option');
    
    if($global_discount_enabled){

        $discount_amount = get_field('global_discount_percent', 'option'); //returns an integer eg 30 for a 30% discount
        if(empty($discount_amount)) return $price;

        //calculate the discounted price
        $price = $price - ($price * ($discount_amount / 100));

    }

   return $price;
}

//We are using hooks for the 'price' and 'sale price'
//Note this means any sale prices will be further discounted by the global discount. Comment out the sale price hooks if you don't want that.
add_filter( 'woocommerce_get_price', 'mytheme_global_sale_price', 10, 2 );
add_filter( 'woocommerce_get_sale_price', 'mytheme_global_sale_price', 10, 2 );
add_filter( 'woocommerce_product_variation_get_price', 'mytheme_global_sale_price', 10, 2 );
add_filter( 'woocommerce_product_get_sale_price', 'mytheme_global_sale_price', 10, 2 );