PHP header redirect after ajax call does not have $_SESSION variables set

Question

I found some jquery and ajax code that gets the browser window width and height. I do not know jquery or ajax, but I was very pleased to get it working, sort of. The script below works perfectly with a link to the next script that needs to run. Both $_SESSION variables are set properly and available. When I link to score.php through a header redirect, the $_SESSION variables apparently are not set because they are null in score.php. Timing issue?

I really do not want to have a link that the user has to click to continue. (These scripts are part of a system that requires a user to be "logged in".) Is there an easy solution to redirect to score.php so that the browserWidth and browserHeight values are available? I am ok with either accessing them as $_SESSION variables or as parameters (score.php?w=$browserWidth&h= . . .).

<?php   
session_start();  
?>  
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">  
<html xmlns="http://www.w3.org/1999/xhtml">  
<head>  
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />  
</head>  
<body>  
<?php  
/******************************************* 
/ code from http://holden.pro/test/test2.php   
/******************************************/   
if(!isset($_POST['width']) || !isset($_POST['height'])) {  
  echo '  
  <script src="//ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>  
  <script type="text/javascript">
  $(document).ready(function () {
    var height = $(window).height();
    var width = $(window).width();
    $.ajax({
      type: \'POST\',
      url: \'get_window_size.php\',
      data: {
        "height": height,
        "width": width
      },
      success: function (data) {
        $("body").html(data);
      },
    });
  });
  </script>
  ';
}

$_SESSION['browserWidth'] =  $_POST['width'];  
$_SESSION['browserHeight'] =  $_POST['height'];  

echo '<a  href="score_image.php">Score Image</a>';    // THIS WORKS!

/*  THIS DOES NOT WROK
$location = 'Location: score_image.php';  
header("$location");  
header("content-type: text/html; charset=utf-8");  
*/
?>  
</body>  
</html>

manish · Accepted Answer · 2014-06-14 21:01:02Z

1

PHP Header - Manual <-- Read for better understanding. Try the code below, it will append the width and height to the URL.

<?php
$width = $_POST['width'];
$height = $_POST['height'];


$host  = $_SERVER['HTTP_HOST'];
$uri   = rtrim(dirname($_SERVER['PHP_SELF']), '/\\');
$extra = 'score_image.php?h='.$height.'&w='.$width;
header('Location: http://'.$host.$uri.'/'.$extra);
exit;
?>

answered Jun 14, 2014 at 21:01

manish

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1 Comment

user2962602 Over a year ago

Your header is certainly better built than mine, however, height and width continue to be null in score.php. I do not think the problem is with the header; rather it seems to be a timing problem. If the script is paused with a link, the width and height can be successfully passed on. If the width and height assignment are immediately followed by the header, it is as if there were never set.

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