>but the OP asked explicitly for a "redirect" to a new page, maybe he needs to have "b.html" appearing in the browser location line?
We don't know.
But most redirect via header() to a local file are nonsense, as include() will work better.
In this case, I am pretty sure he asked for redirection due to the fact that he didn't know the solution via include().
And (most important): if you do a header() or meta-Tag for redirection, then(!) the variables are NOT interpreted by PHP.