PHP-How to solve that Html Page Source is appending to the download file

I am downloading a file from Ftp folder after upload.

Problem is when i open the txt file it show s html page source appending with file content

If i preview image file(jpg or jpeg) it shows image is corrupted

If i open pdf error: Failed to load Pdf document

Please let me know where i am wrong.

Here is my code:

if (isset($_GET['id']) && basename($_GET['id']) == $_GET['id']) {
    $filename = $_GET['id'];
} else {
    $filename =NULL ;
}

$err = 'Sorry, the file you are requesting is unavailable.';
if (!$filename) {
    // if variable $filename is NULL or false display the message
    echo $err;
} else {
    // define the path to your download folder plus assign the file name
    $path = '/home/devestctrl/public_html/wp-content/uploads/'.$filename;
    // check that file exists and is readable
    if (file_exists($path) && is_readable($path)) {
        // get the file size and send the http headers
        $size = filesize($path);
        header('Content-Type: application/octet-stream');
        header('Content-Type: '.$mime);
        header('Content-Length: '.$size);
        header('Content-Disposition: attachment; filename='.$filename);
        header('Content-Transfer-Encoding: binary');
        // open the file in binary read-only mode
        // display the error messages if the file can´t be opened
        $file = @ fopen($path, 'rb');
        if ($file) {
            // stream the file and exit the script when complete
            fpassthru($file);
            exit();
        } else {
            echo $err;
        }
    } else {
        echo $err;
    }
}

I checked by using echo of $filename;

It shows the output in the file instead of printing in page.

error displays:

Sorry, the file you are requesting is unavailable.

After error also i can download, but echoed $filename displayed in file.

Insert into table:

 echo "<tr><a href='?id=" . $row["FileupName"]. "'>".$row["FileupName"]."</td></tr>";