woocommerce_vat_countries │ filter-hook │ WC 1.0

Usage

add_filter( 'woocommerce_vat_countries', 'wp_kama_woocommerce_vat_countries_filter' );

/**
 * Function for `woocommerce_vat_countries` filter-hook.
 * 
 * @param  $array_merge 
 *
 * @return 
 */
function wp_kama_woocommerce_vat_countries_filter( $array_merge ){

	// filter...
	return $array_merge;
}

$array_merge

-

Where the hook is called

return apply_filters( 'woocommerce_vat_countries', array_merge( $eu_countries, $vat_countries ) );

Where the hook is used in WooCommerce