在Drupal获取一个自定义字段的值最常用的方法是：
$nianling = $node->field_nianling[LANGUAGE_NONE][0]['value'];
不过当field_nianling内容为空时，会出现类似这样的错误： Notice: Undefined index: value in eval() ，如果我们在在取值之前加个判断，如这样：
if (isset(field_nianling[LANGUAGE_NONE])) {
$nianling = $node->field_nianling[LANGUAGE_NONE][0]['value'];
}
是可以解决问题，但如果字段多时，代码看起来就不够简洁，而且如果自定义字段是列表字段，就有可能还需要根据列表的 key 获取相应的 value 值。那么有没有更好的方法来获取自定义字段的值呢？
Drupal已经给我们提供了一个 <a href="https://api.drupal.org/api/drupal/modules%21field%21field.module/function/field_get_items/7">field_get_items</a> 函数，原型如下：
function field_get_items($entity_type, $entity, $field_name, $langcode = NULL)
函数说明：
返回当前语言的此字段项目。
参数：
$entity_type: The type of $entity; e.g., 'node' or 'user'.
$entity: The entity containing the data to be displayed.
$field_name: The field to be displayed.
$langcode: (optional) The language code $entity->{$field_name} has to be displayed in. Defaults to the current language.
Return value
An array of field items keyed by delta if available, FALSE otherwise.
得到了 field_get_items 的返回字段项目，就可以使用 <a href="https://api.drupal.org/api/drupal/modules!field!field.module/function/field_view_value/7">field_view_value</a> 来渲染单个项目值：
field_view_value($entity_type, $entity, $field_name, $item, $display = array(), $langcode = NULL)
Returns a renderable array for a single field value.
Parameters
$entity_type: The type of $entity; e.g., 'node' or 'user'.
$entity: The entity containing the field to display. Must at least contain the id key and the field data to display.
$field_name: The name of the field to display.
$item: The field value to display, as found in $entity->field_name[$langcode][$delta].
$display: Can be either the name of a view mode, or an array of display settings. See field_view_field() for more information.
$langcode: (Optional) The language of the value in $item. If not provided, the current language will be assumed.
<strong>返回值 </strong>指定字段的渲染数组
下面是一个显示 field_jinsheng 字段的例子代码：
$jinsheng = field_get_items('node', $node, 'field_jinsheng');
$output = field_view_value('node', $node, 'field_jinsheng', $jinsheng[0]) ;
$output = drupal_render( $output);
print $output;