title: 2 DateTimes are getting editted by 1
body: <p>Ok i got a weird issue here.
  Im trying to calculate the old date and the new date. However i spotted a issue that is unexplainable by me.</p>
  
  <p><strong>The setup :</strong><br>
  I have 2 new dates set on today.</p>
  
  <pre><code>$tempstamp = new DateTime();
  $newstamp = new DateTime();
  </code></pre>
  
  <p>Now, i edit the newstamp into a new date useing :</p>
  
  <pre><code>if ($newstamp -&gt;format('His') &gt; 120000) $newstamp -&gt;modify('+7 day');
  else $newstamp -&gt;modify('+4 day');
  </code></pre>
  
  <p>Which works perfectly. However now comes the weird part.
  When i dump both values before and after it the tempstamp gives a unexplainable value :</p>
  
  <pre><code>case '2':
    $tempstamp = $newstamp;
  
    dump($tempstamp-&gt;format('m-d')); // 02-19 - CORRECT
    dump($newstamp-&gt;format('m-d')); // 02-19 - CORRECT
  
    if ($newstamp-&gt;format('His') &gt; 120000) $newstamp-&gt;modify('+7 day');
    else $newstamp-&gt;modify('+4 day');
  
    dump($tempstamp-&gt;format('m-d')); // 02-26 - FALSE
    dump($newstamp-&gt;format('m-d')); // 02-26 - CORRECT
  </code></pre>
  
  <p>*NOTE: dump is our way of var_dumping*</p>
  
  <p><strong>The Question:</strong><br>
  Can someone explain why tempstamp is getting editted as well while i only edit newstamp?</p>