SOLVED DB connection from different domain/subdomain

Hi,

I'm trying to install Wordpress (via Softaculous) in a subdomain (new.domain.com).
DB connection is not working, even with the testdb file.

PHP:

<?php
$link = mysqli_connect('localhost', 'db_user', 'db_password');
if (!$link) {
die('Could not connect: ' . mysqli_error());
}
echo 'Connected successfully';
mysqli_close($link);
?>

The very same file works from the main domain (www.domain.com)

What can I check to solve this?

Thank you.

 

Hi,

Actually, it begun working the day after.
Might have been a DNS propagation delay or something like that, following your insight.

Thank you very much.