I have a little problem with my apache centos server with php 5.0 and mysql. When I open multiples files, sometimes, it show de pages .php for download. I think that PHP have a problem, because it happens only when I open many browser windows (like 30). How can I solve this issue?
When you download the page, what do you see in the file you downloaded? I bet you'll find some kind of error message.
The problem is probably that opening many windows creates some kind of error condition, and the PHP code that generates the error message for that condition fails to output a proper HTTP header. Without a proper HTTP header, the browser doesn't know that it is supposed to display the error message and instead offers you to download it.