PHP - 对数组中的一个键使用函数

I'm creating one simple blog script and I have this problem:

In MySQL I'm saving PostDate as TIMESTAMP, and when I select from MYSQL PostDate looks like this 2015-10-25 13:53:35, but I want to convert this timestamp to H:M D-M-Y. I'm created one function for converting but I don't know how to use it for key PostDate in array. Exactly I want to rewrite all PostData keys in array to new format. I know how to do it with foreach loop but I cant do this because I use Smarty Template Engine.

ConvertTimestamp():

public function ConvertTimestamp($Timestamp)
{
  $TimeDate = explode(' ', $Timestamp);
  $Date = explode('-', $TimeDate['0']);
  $Date = $Date[2].'-'.$Date['1'].'-'.$Date['0'];
  $Time = explode(':', $TimeDate['1']);
  $Time = $Time['0'].':'.$Time['1'];
  $TimeDate = $Time.' '.$Date;
  return $TimeDate;
}

this format 2015-10-25 13:53:35 is called datetime format not TIMESTAMP .

But anyway , to convert datetime to any format you want you can do this at mysql side . Suppose the table you select the data from is called "test_table" and has a datetime field called PostDate in that table which you want to convert to this format H:M D-M-Y ( which is what you want ) , you can do the following query :

SELECT DATE_FORMAT(PostDate,'%H:%M %D-%M-%Y') FROM `test_table`