Retrieving display name in php

Hi everyone,
I’m trying to retrieve the display_name field from the wp_users table using a standalone php script (not using wordpress functions).

It works fine but I have few users with “strange characters” display names such as: “〖ƝƁƘ〗” (it’s a gaming site so people uses “clan tags”.

In such cases che display name returns a series of question marks (???????).

Both in DB and in WordPress display names are correctly displayed.
I cannot find how to diplay them correctli in my standalon php script.

Tried to switch content type in HTML from “charset=iso-8859-1” to “utf-8” but this does not change nothing.

Who can help?

Thank you!!!