WordPress | Convert #038; to &

I need to pass a variable inside the permalink that takes me to my custom post, and then execute the $_GET of this variable inside an input of my cf7.

The only problem WordPress encodes the & in #038;

I tried to decode the special characters but nothing.

Browsing the net, I found on another question here on stackoverflow, the possibility of using: html_entity_decode

But if I echo in frontend, it works perfectly, but when I click on the link it is converted back to: #038;

example:

<?php
$url="?r=".$prezzo_finale.html_entity_decode('&#038;').'s=".$art_p;
echo $url;
?>

return me in frontend with echo: ?r=405&s=Sito Web

but when i click on my post the permalink is: /?r=405#038;s=Sito%20Web

To pass the variable inside my post I use this structure:

<div class="card" id="professionista<?= $query->post->ID ?>" style="cursor: pointer;">

<!-- CODE -->

<script type="text/javascript">
document.getElementById("professionista<?= $query->post->ID ?>").setAttribute("onclick', 'location.href = "<?php echo esc_url( get_permalink($query->post->ID).$url ); ?>"');
</script>
</div>

How can I get this converted?

You’re setting the link using PHP-generated JavaScript. I’m sure there are better ways to do this, e.g. just write the onclick handler into the div, or use an <a> tag for a link as usual, but if you want to it this way you should be using esc_js() not esc_url().

<script type="text/javascript">
document.getElementById("professionista<?= $query->post->ID ?>").setAttribute(
  'onclick', 'location.href = "<?php echo esc_js( get_permalink($query->post->ID).$url ); ?>"');
</script>

As also discussed in the comments you should probably also be using add_query_arg() to append the &s= part to your URL, rather than just string concatenation. That would also handle the urlescape-ing the value part of $url if you’re not doing that already, and would cope with the case where your permalink doesn’t contain a ? already which it looks like you’re assuming.