Thread:Project:Support desk/Loading HTML/Wiki code in system message?

Simple problem - I'm loading a system message (Eg, Mediawiki:titlehere).

Long story short - "Mediawiki:titlehere" uses some HTML, which I'd like to load onto the login page via PHP (Re-working the login page include a birthdate, which is entered into the database and can used against the user (Such as limited what they can/can't do)

However, when attempting to do so, the message is instead loaded as raw, un-parsed text.

Anytime I look up anything about this, I get the opposite results: "How do you load PHP in HTML?"

So, how exactly would I manage to display HTML/Wiki code in a system message loaded in PHP? The file in question is Usercreate.php.