CiviCRM - implementation of hook_civicrm_buildForm() to remove required billing address fields.

gistfile1.txt

/**
 * Implements hook_civicrm_buildForm().
 */
function example_civicrm_buildForm($formName, &$form) {
  switch ($formName) {
    case 'CRM_Contribute_Form_Contribution_Main':
      $fields_not_required = array(
        'billing_first_name',
        'billing_middle_name',
        'billing_last_name',
        'billing_street_address-5',
        'billing_city-5',
        'billing_state_province_id-5',
        'billing_postal_code-5',
        'billing_country_id-5',
      );
      foreach ($fields_not_required as $field) {
        $form->_paymentFields[$field]['is_required'] = FALSE;
      }
      break;
  }
}