File Downloading error from database php - php

Question

I have read every tutorial I can find on this topic, but none of them helped fix my issue. I don't know why, but my code is just giving me an html file whenever I click on the download button, instead of downloading an image file.
HTML:
Download Now
PHP:
<?php
$id= $_GET['id'];
$con= mysqli_connect("localhost","root","","dbname");
if (mysqli_connect_errno($con))
{
echo "<script type=\"text/javascript\">alert('Failed To connect to MySQL: "+"mysqli_connect_error();"+"');</script>";
}
else
{
$sql = "SELECT * FROM users_files WHERE file_id = ".$id;
$result = mysql_query($sql);
$row_cnt = mysqli_num_rows($result);
echo "<script type=\"text/javascript\">alert('".$row_cnt."');</script>";
if(!$result || !mysql_num_rows($result)){
echo "<script type=\"text/javascript\">alert('Invalid file chosen.');</script>";
//echo '<script language="javascript" type="text/javascript" >';
//echo ' window.location.assign("ViewMyFiles.php");';
//echo '</script>';
mysqli_close($con);
}
$curr_file = mysql_fetch_assoc($result);
$size = $curr_file['file_size'];
$type = $curr_file['file_type'];
$name = $curr_file['file_name'];
$content = $curr_file['file_content'];
header("Content-length: ".$size."");
header("Content-type: ".$type."");
header('Content-Disposition: attachment; filename="'.$name.'"');
readfile($content);
$_SESSION['email']=$nemail;
mysqli_close($con);
}
?>
I named the above PHP file getfile.php and I'm getting on download result as getfile.htm.

Answer 1

Debug!
Comment out the headers and see, what really gets to the client. Then comment them in and check in browser dev console (header + response).
You're also vulnerable to SQL injections.