title: Should I use Form::submit to pre-fill form with session variables?
body: <p>I'm pretty new to both PHP and symfony, and I'm looking at the code written by one of my co-workers.
  it's a simple inquiry form which has confirm page. it should remember what user entered even if the user go back from confirm pagn.
  He uses session to store posted data, and Form::submit to fill the data a user previously entered (such as name, e-mail address, message body).</p>
  
  <p>It works, but is it good idea to use this technique? Is there any downside to do this?</p>
  
  <p>First, I can no longer use Form::isSubmitted to check if the user submitted the form (as manually calling submit() makes this flag true), though I could still use isMethod('POST').</p>
  
  <p>Second, official doc uses DB instead of session to store temporary variable.
  Is it good or bad to store temp data in the session?
  <a href="https://symfony.com/doc/current/forms.html" rel="nofollow noreferrer">https://symfony.com/doc/current/forms.html</a></p>
  
  <p>I've read somewhere in stackoverflow that submit will be deleted in 3.0, but it's still there, even in official 4.0 doc.</p>