File Download with PHP gives error

Question

Note: I have tried to implement the solutions provided in : How to fix "Headers already sent" error in PHP and it didnot help so I have posted this question. I have gone through various posts on similar problem but none of the solutions worked. Following is my code:

<form role="form" method="POST">
 <input type="submit" name="dff" id="dff" class="btn btn-default" value="Download Franchisee Form"></input>
</form>
<?php
 if(isset($_POST['dff']))
 {
  $yourfile="MyFile.pdf";
  $fp = @fopen($yourfile, 'rb');
  if (strstr($_SERVER['HTTP_USER_AGENT'], "MSIE"))
  {
    header('Content-Type: "application/octet-stream"');
    header('Content-Disposition: attachment; filename="yourname.file"');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header("Content-Transfer-Encoding: binary");
    header('Pragma: public');
    header("Content-Length: ".filesize($yourfile));
  }
  else
  {
    header('Content-Type: "application/octet-stream"');
    header('Content-Disposition: attachment; filename="yourname.file"');
    header("Content-Transfer-Encoding: binary");
    header('Expires: 0');
    header('Pragma: no-cache');
    header("Content-Length: ".filesize($yourfile));
  }
  fpassthru($fp);
  fclose($fp);
 }
?>

I get following errors on clicking this button:

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 133

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 134

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 135

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 136

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 137

Warning: Cannot modify header information - headers already sent by (output started at C:\xampp\htdocs\GoogleKids\Franchisee.php:116) in C:\xampp\htdocs\GoogleKids\Franchisee.php on line 138

and after that, I get unreadable symbols on the web page something like below:

%PDF-1.5 %���� 1 0 obj <> endobj 2 0 obj <> endobj 3 0 obj <>/ExtGState<>/Font<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 595.32 841.92] /Contents 7 0 R/Group<>/Tabs/S>> endobj 4 0 obj <> stream ����JFIF``��ZExifMM*JQQ�Q�������C    !(!0*21/*.-4;K@48G9-.BYBGNPTUT3?]c\RbKSTQ��C''Q6.6QQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQQ��d9"�� ���}!1AQa"q2���#B��R��$3br� %&'()*456789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz��������������������������������������������������������������������������� ���w!1AQaq"2�B���� #3R�br� $4�%�&'()*56789:CDEFGHIJSTUVWXYZcdefghijstuvwxyz����

Note: Even I used ob_start() and ob_flush() at the beginning and end of the script respectively, still i got the same error.

Note: I have not used any other PHP script on complete page. This is the only script. However, I do have another form tag that links to another webpage on performing action and it has its own separate submit button with a unique name and id. Please help.

Answer 1

Try the following solution: On your web page, remove form tag and use an anchor as below:

<a href="downloads.php?download_file=MyFile.pdf">Download The File</a>

Then, create a new file named downloads.php and write the following code:

<?php
ignore_user_abort(true);
set_time_limit(0); // disable the time limit for this script

$dl_file = preg_replace("([^\w\s\d\-_~,;:\[\]\(\).]|[\.]{2,})", '', $_GET['download_file']); // simple file name validation
$dl_file = filter_var($dl_file, FILTER_SANITIZE_URL); // Remove (more) invalid characters
$fullPath = $dl_file;

if ($fd = fopen ($fullPath, "r")) {
    $fsize = filesize($fullPath);
    $path_parts = pathinfo($fullPath);
    $ext = strtolower($path_parts["extension"]);
    switch ($ext) {
        case "pdf":
        header("Content-type: application/pdf");
        header("Content-Disposition: attachment; filename=\"".$path_parts["basename"]."\""); // use 'attachment' to force a file download
        break;
        // add more headers for other content types here
        default;
        header("Content-type: application/octet-stream");
        header("Content-Disposition: filename=\"".$path_parts["basename"]."\"");
        break;
    }
    header("Content-length: $fsize");
    header("Cache-control: private"); //use this to open files directly
    while(!feof($fd)) {
        $buffer = fread($fd, 2048);
        echo $buffer;
    }
}
fclose ($fd);
exit;
?>

I tested this code, it worked perfect for me in Chrome as well as IE. Make sure you change the file name and the file path according to your requirements. Don't forget to vote if this helps you.

Answer 2

You have...

<html><?php
    header('...');
?>

You want...

<?php
    header('...');
?><html>

The only code that may occur before a PHP header(...) call is more PHP (or any server-side code), not HTML, CSS, or plaintext. For the server to send any content, it must send the headers, and once sent, they cannot be resent. So, you must set the headers before sending content.