Making WooCommerce coupon codes work with accented - special - characters

gistfile1.txt

// Tested with Turkish letters like İ or Ğ, should work with other languages as well like German Ç or Czech Č etc. etc.

add_filter( 'woocommerce_coupon_code', 'make_coupons_case_insensitive' );

function make_coupons_case_insensitive( $coupon_code ) {
    // Convert special characters to ASCII
    $coupon_code = iconv('UTF-8', 'ASCII//TRANSLIT', $coupon_code);
    // Change all coupon codes to lowercase
    return strtolower( $coupon_code );
}