Request password on file_download with Advanced Custom Fields - php

Question

So what I want is to request a password when downloading files that are dynamically uploaded via wordPress-plugin Advanced Custom Fields.
I can't get it working, and here's my code:
html:
<div class="documentWrap">
<?php while ( have_posts() ) : the_post(); ?>
<?php get_template_part( 'content', 'page'); ?>
<?php if(get_field('dokumentgrupp')): ?>
<?php while(has_sub_field('dokumentgrupp')): ?>
<div class="docGroup clearfix">
<h2><?php the_sub_field('gruppnamn'); ?></h2>
<?php if(get_sub_field('filer')): ?>
<?php while(has_sub_field('filer')): ?>
<ul>
<li>
<h3><?php the_sub_field('filnamn'); ?></h3>
ladda ner
<!div id="passWrap">
<div id="passBox">
<?php // if( get_field('password') ): ?>
<form method="post">
<input name="pass" type="password" action="download_pw.php">
<input type="submit" name="submit" value="ladda ner">
</form>
</div>
<?php //endif; ?>
</div>
</li>
</ul>
<?php endwhile; ?>
<?php endif; ?>
</div>
<?php endwhile; ?>
<?php endif; ?>
</div>
<?php endwhile; ?>
</div>
download_pw.php:
<?php
$pw = md5($_POST['pass']);
$valid_pw = md5(get_sub_field('password'););
$file_url = get_sub_field("fil_url");
if {$pw != $valid_pw) {
echo 'Tyvärr har du inte tillgång till denna fil';
}else{
header('Location: $file_url');
}
?>

Answer 1

If you are using this HTML on the front end, how about just using the built in password protection on the page/post showing the file?
Wordpress Codex: Using Password Protection
If that's not an option, how about trying something like this: https://wordpress.stackexchange.com/questions/37144/how-to-protect-uploads-if-user-is-not-logged-in