What exactly do you mean by "new Page B class ... with a class B1?" Do you mean that Page B has a B1 as in a one-to-one database relationship?
How all this will work for you will depend on the actual names of your classes. You need to do a ?flush=1 once you've added your classes, of course. You also need to make sure the autoloader, with the help of the manifest builder, is going to find your classes. I'm no expert on exactly what will and won't be found, but note this from [url=http://doc.silverstripe.org/doku.php?id=manifestbuilder]the manifest builder documentation[/url]:
"If your class contains an underscore, for example, Page_Controller, then the filename is expected to be the stuff before the underscore. In this case, Page.php.''
thank you for your reply.
With Page B class , I mean class SpecialDataPage extends Page and into the same file I specified B1 class extend Image and B2 class was putted before Product Class into the same php file.
All works before I created SpecialDataPage.
Do you think the problem was class name ( class Resize_Image extends Image & class Banner_Image extends Image )?