is there some function in PHP that does exactly the opposite of htmlspecialchars()?

In Kev's tutorial, under chapter .. Contetn Formatting, is explained how to define custom "tags" for your cms. In the beginning he uses htmlspecialchars to get rid of those < and > etc.

But I thought it could be useful if there was a tag
HTML Code:
that allows the writer of the article to put in some regular html, that would be parsed as regular html, and not as text.

But to achieve this, I need to reverse &lt; to < etc. And therefore I want a function like htmlregularchars or so.

Does that exist?