title: gRPC Protobuf's Timestamp.FromDateTime() returns null on PHP
body: <p>I cant get my head around what I am doing wrong here.</p>
  
  <pre><code>use Google\Protobuf\Timestamp;
  
  $timestamp = new Timestamp();
  $dt = Carbon::now();
  $pt = $timestamp-&gt;fromDateTime($dt);
  </code></pre>
  
  <p>Carbon is a simple PHP API extension for DateTime so it should work but instead I get a null value for $pt</p>