title: php Object of class DateInterval could not be converted to string
body: <p>i've tried using date_diff and date_create to get a difference from two date that's already converted to string.</p>
  
  <p>here's the code:</p>
  
  <pre><code>$date_1 = date_create();
  $date_now = date_format($date_1, 'Y-m-d');
  
  
  //echo $date_now . "\n";
  $date=date_create($date_now);
  date_add($date,date_interval_create_from_date_string("3 days"));
  $date_return =  date_format($date,"Y-m-d");
  
  
  $diff = date_diff(date_create($date_now), date_create($date_return));
  
  echo $diff;
  </code></pre>
  
  <p>and i am getting this error:</p>
  
  <pre><code>Object of class DateInterval could not be converted to string
  </code></pre>