Questions about MathML...

Hello, 
I want to use MathML in dynamic page (php).
At the head of my php page, I header("Content-type:text/xml");
I don't know whether what I have done is right or not, but it can work well in some simple test.

But.....
When there are some special strings like "±", "−", the page cannot pass the xml regular.
Another similar problem, I can't use   in the page.

I have some javascript in the page, it can't pass the xml regular, either.

How to solve them?


by G.M.O. Bug