PHP页面刷新问题

I am working on an Online Quiz.
On every click of the 'next question' button, I have tried the following:

if(isset($_POST['submit']) && isset($_POST['ans']))
{
  //process answers and fetch next question
  //Increment the Session variable which contains serial of next question
  $_SESSION['qnum'] = $_SESSION['qnum']+1;
}

Whenever I click on the F5 button, the session gets updated and a new question is fetched.
The session should be incremented only when the next question button is clicked, otherwise it should not be increment.
The following is what I have tried after referring to an article:

$pageWasRefreshed = isset($_SERVER['HTTP_CACHE_CONTROL']) && $_SERVER['HTTP_CACHE_CONTROL'] === 'max-age=0';
if($pageWasRefreshed) 
{
  //refetch the current question.
}
else
{
 //refetch the current question and increment the Session Variable 
}

This approach worked fine in Mozilla Firefox
In IE, both the button click and F5 hits are taken as not refreshed
In Chrome, both the button click and F5 are taken as refreshed

I have tried some other variations from other articles on StackOverflow and Google, but those didn't work at all including an ajax based solution.

You should never display a page that was requested with POST.

What you do, is process the POST data, then refresh the page with php.

Like this:

<?php
if($_SERVER['REQUEST_METHOD'] === 'POST') {
  //handle the POST data
  ...

  // now refresh
  header('location: index.php');  // or what ever url you were on
  exit();
}
// else: show the page
echo '<html> ...';
?>

Notice: if you use header('location: ...') NOTHING must be printed/echoed, not even a space / new line / ...

So the first character of your .php file must be "<" (of the of the opening php tags)

May not be the perfect solution but will work

if(isset($_POST['submit']) && isset($_POST['ans']))
{
  //I am assuming we have question id or any  uniq data about question
  if($_SESSION['last_que'] != $_POST['que_id']){
      $_SESSION['qnum'] = $_SESSION['qnum']+1;
      $_SESSION['last_que'] = $_POST['que_id'];
  }

}

If you want to prevent counting all the pages just use arrays and array_search

Following should be your best solution:

$RSig = md5($_SERVER['REQUEST_URI'].$_SERVER['QUERY_STRING'].print_r($_POST, true));

    if(isset($_SESSION['LastRequest']) && $_SESSION['LastRequest'] == $RSig)
    {
        $_SESSION['reqstat']='refresh';
    }
    else
    {
        $_SESSION['qnum'] = $_SESSION['qnum']+1;
        $_SESSION['reqstat']='newrequest';
        $_SESSION['LastRequest'] = $RSig;
    }

You can use the Session: reqstat to check do thing that is supposed to be done on button click and not on refresh.