title: set datetime value in input html from php
body: <p>I just try to set a value datetime for input( It is for change the current value of variable date time), but my html show an error ( seems it's fault about the format):</p>
  
  <p>the code is :</p>
  
  <p><code>&lt;input type="datetime" name="deadline" required value ='&lt;?php echo date('c', $dateDeadline); ?&gt;'/&gt;</code></p>
  
  <p>Thx a lot. </p>