Why might htmlspecialchars_decode not work?

Question

PHP

The situation is this:
I am writing my ticket system for the user's personal account. I accept the text of the message from the user,
convert the inserted links into clickable ones, and then convert the html tags into HTML entities.

$text = preg_replace("/\b((http(s?):\/\/)|(www\.))([\w\.]+)([\/\w+\.]+)([\?\w+\.\=]+)([\&\w+\.\=]+)\b/i", "<a href=\"http$3://$4$5$6$7$8\" target=\"_blank\">$2$4$5$6$7$8</a>", $text);
$text = htmlspecialchars($text);

the data gets into mysql DB
When I display messages in a loop, before printing out the $text variable, I process it with the htmlspecialchars_decode() function;
but unfortunately, when I open the source code of the page with the list of messages, I see:

<a href="https://vk.com/" target="_blank">https://vk.com/</a>

Explain to me, stupid, why they don’t convert back and how to make links clickable then?