在functions.php中添加woocommerce货币功能会导致白屏死机

将以下函数添加到我的functions.php文件中导致白屏死机。当我删除此功能时，网站显示良好:

add_filter( 'woocommerce_currencies', 'add_my_currency' );
function add_my_currency( $currencies ) {
  $currencies['KES'] = __( 'Kenyan Shillings', 'woocommerce' );
  return $currencies;
}
add_filter('woocommerce_currency_symbol', 'add_my_currency_symbol', 10, 2);
function add_my_currency_symbol( $currency_symbol, $currency ) {
   switch( $currency ) {
      case 'KES': $currency_symbol = 'KSH'; break;
   }
   return $currency_symbol;
}