Landstrasse

function receipt_meta_box_currency(){
    $form = tr_form();

    echo $form->select('receipt_currency', array(
        'class' => 'receipt_currency'
    ), array(
        'label' => ' '
    ))
    ->setOptions(array(
        'US Dollar' => 'USD',
        'EURO' => 'EUR',
        'Schweizer Franken' => 'CHF'
    ))
    ->setDefault('CHF');
  }


  add_action('receipt_meta_box', function( $post_type ){
    $box = tr_meta_box('meta-box_currency', null, array(
        'label' => 'Währung'
    ))
    ->setCallback('receipt_meta_box_currency')
    ->setContext('side');

    $box->apply($post_type);
  }, 10);