title: Apache ERR_EMPTY_RESPONSE without any data in the log
body: <p>i have a website and when the user fills a form, the response code is ERR_EMPTY_RESPONSE.</p>
  
  <p>The problem is there is no information in the Apache logs.</p>
  
  <p>The project is done with Symfony2 over Apache on Linux.</p>
  
  <p>I don't know if there is a problem with APC,but it is difficult to track if there is no errors in the log.</p>
  
  <p>Any ideas?</p>