woocommerce_coupon_is_valid filter-hook . WC 1.0

Usage

add_filter( 'woocommerce_coupon_is_valid', 'filter_function_name_7578', 10, 3 );
function filter_function_name_7578( $true, $coupon, $that ){
	// filter...

	return $true;
}

$true

-

$coupon

-

$that

-

Where the hook is called

if ( ! apply_filters( 'woocommerce_coupon_is_valid', true, $coupon, $this ) ) {

Where in WP core the hook is used WooCommerce