对象内部的PHP访问字符串

我有一个数组：

array(2) (
  [0] => DMV\DrvrEdBundle\Entity\INSTRUCTOR object {
    id => (int) 22
    Instructor_Lic => (string) 67890
    First_Name => (string) lkioli
    Last_Name => (string) oioiodfdfd
    Email => (string) ioii@dfdd.dfd
    Status => (string) ACTIVE
    CreationDate => DateTime object {
      date => (string) 2014-05-20 09:46:03
      timezone_type => (int) 3
      timezone => (string) America/New_York
    }
    EditDate => DateTime object {
      date => (string) 2014-05-20 09:46:14
      timezone_type => (int) 3
      timezone => (string) America/New_York
    }
  }
)

我想访问CreationDate对象中的日期字符串。我怎样才能访问这个

任何帮助都将不胜感激

---迈克

只是：

$arr[0]->CreationDate->format('Y-m-d H:i');
     ^--------- index of array 

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谢谢你的回答，皮奥特