wordpress feed增加自定义字段

function fix_for_360_rss2_item() {
$fields = array('_addlink_info_gglink');
$post_id = get_the_ID();
foreach($fields as $field){
if ($value = get_post_meta($post_id,$field,true)){
if($field == '_addlink_info_gglink'){
$field = 'packagename';
preg_match('/id=(.*)&/', $value, $r);
if($r && !empty($r[1])){
echo "<{$field}><![CDATA[{$r[1]}]]></{$field}>\n";
}
}
}
}
}
add_action('rss2_item', 'fix_for_360_rss2_item');