title: MongoDB BSON Date - formatting options in PHP toDateTime() method
body: <p>The documentation from the official PHP site is sorely lacking:
  <a href="http://php.net/manual/en/mongodb-bson-utcdatetime.todatetime.php" rel="nofollow">http://php.net/manual/en/mongodb-bson-utcdatetime.todatetime.php</a></p>
  
  <p>The examples given have parameters for formatting as 'r' and 'U.u'. These give outputs:</p>
  
  <pre><code>string(31) "Fri, 07 Oct 2016 10:40:01 +0000"
  string(17) "1475836828.000000"
  </code></pre>
  
  <p>I can't seem to find any documentation for these. My question is, what parameter do I need to specify to get the datetime as a string in the following format:</p>
  
  <pre><code>"D-m-y H:i:s"
  </code></pre>