Pdf file is not downloading with php using header()

Question

I want the user to be able to download some files I have on my server, but when I try to download file shows error like below.

code

 public function saveattachment(){
    $fn=$this->input->get_post('fn');
    $userid=$this->input->get_post('autherid');
    $file_url = realpath("./private").$userid."/".$fn;
    $file_name =basename($file_url);
    $ext = explode(".", $file_name);

    switch($ext[sizeof($ext)-1])
    {
        case 'jar': $mime = "application/java-archive"; break;
        case 'zip': $mime = "application/zip"; break;
        case 'jpeg': $mime = "image/jpeg"; break;
        case 'jpg': $mime = "image/jpg"; break;
        case 'jad': $mime = "text/vnd.sun.j2me.app-descriptor"; break;
        case "gif": $mime = "image/gif"; break;
        case "png": $mime = "image/png"; break;
        case "pdf": $mime = "application/pdf"; break;
        case "txt": $mime = "text/plain"; break;
        default: $mime = "application/force-download";
    }

    header('Content-Description: File Transfer');
    header('Content-Type: '.$mime);
    header('Content-Disposition: attachment; filename='.basename($file_name));
    header('Content-Transfer-Encoding: binary');
    header('Expires: 0');
    header('Cache-Control: must-revalidate, post-check=0, pre-check=0');
    header('Pragma: public');
    header('Content-Length: ' . filesize($file_url));   
    ob_clean();
    flush();
    echo $file_url;
    }

The file is downloaded but its not opening.

Answer 1

header() must be called before any actual output is sent, Sample Code

<?php
header("Content-type:application/pdf");

// It will be called file_name_for_download.pdf
header("Content-Disposition:attachment;filename='file_name_for_download.pdf'");

// The PDF source is file_for_read.pdf
readfile("file_for_read.pdf");
?>

In your case use basic code and make sure its working fine, then add additional code as per requirements

Answer 2

Replace echo $file_url; by readfile($file_url);

Answer 3

I got it. I had coded as header('Content-Length: ' . filesize($file_url)); and i replaced this by header('Content-Length: ' . filesize($file_name)); . Now its working. Thanks all for your time to help me.