I am trying to implement Stack Exchange using oAuth 2.0. I am able to get CODE but, when I try to get `access_token` through this code:

<!-- language: lang-php -->

    <?php
    if(isset($_GET['code']))
    {
    ?> 
    <form method="POST" action="https://stackexchange.com/oauth/access_token" enctype="application/x-www-form-urlencoded">
    <input type="hidden" name="client_secret" value="aaaaaaaaaaaaaaaaaaaaaaaa" />
    <input type="hidden" name="code" value="<?php echo $_GET['code'];?>" />
    <input type="hidden" name="client_id" value="0000" />
    <input type="hidden" name="redirect_uri" value="http%3A%2F%2Fmysite.com%2Fmypage.php" />
    <input type="submit" name="submit" value="stack" />
    </form>

    <a href="https://stackexchange.com/oauth/access_token?client_id=0000&client_secret=aaaaaaaaaaaaaaaaaaaaaaaa&code=<?php echo $_GET['code'];?>&redirect_uri=http%3A%2F%2Fmysite.com%2Fmypage.php">abcd</a>
    <?php
    }
    ?>

when I click on anchor tag nothing happens, it just stays on may page only.

When I submit the form, `ACCESS_TOKEN` is displayed on  
`https://stackexchange.com/oauth/access_token`  
but its not redirecting back to my `redirect_uri`. 

If anyone can guide me, it will be very helpful.