致命错误:不能使用classname类型的对象作为数组

我有一个数组:

 Array
(
[0] => BugHerd_Project Object
    (
        [id:BugHerd_Project:private] => 24323
        [name:BugHerd_Project:private] => bugherd a
        [devurl:BugHerd_Project:private] => http://st.com/a/
        [active:BugHerd_Project:private] => 1
        [created:BugHerd_Project:private] => DateTime Object
            (
                [date] => 2014-05-03 11:15:22
                [timezone_type] => 2
                [timezone] => Z
            )
        [updated:BugHerd_Project:private] => DateTime Object
            (
                [date] => 2014-05-05 06:55:52
                [timezone_type] => 2
                [timezone] => Z
            )
    )
)

1。我访问这个数组的代码是:

• 在这个代码中我只是从api获取数据。它的简单http认证代码
• 我使用php包装这里是链接:https://github.com/spekkionu/bugherd.

• 从他们提到的api文档:curl -u api_key:x https://www.bugherd.com/api_v2/projects/1.json

   $api = new BugHerd_Api($email,$password);
  $projects = $api->listProjects();
  $i=0;
  on  doing print_r($projects[$i]['id:BugHerd_Project:private']);