Redirect

<?php

session_start();

if(isset($_POST['app_id'])) {
  $app_id = $_POST['app_id'];
  $code = $_POST['code'];
  $secret = $_POST['secret'];

  echo "<script type=\"text/javascript\">
          window.open('https://connect.deezer.com/oauth/access_token.php?app_id=".$app_id."&secret=".$secret."&code=".$code."', '_blank')
      </script>";

}

?>