Can i have old files in a site which will not be included in link?

[tenzin]

hi everyone,
yet again, in my workplace, an old site has been changed vastly. the site has been ranking very well in google and is still ranking good. but now it will lose its rank in SE for sure. actually, the site was static previously. so, now the pages are changed from .html file to .php file. so, to save the PR, my boss came up with an idea to include the old files in the site but not put them in links. so, when opening the site and going thru links those wont come up but when someone types those file name manually, those will come up. so, is this idea good? so as to save the PR. i am hesitating to use 301 redirect tag. actually i dont know how to use it

[leftybogs]

maybe this can help 301 redirection

[tenzin]

maybe this can help 301 redirection

Thank you leftybogs!!! U have always answered me
i just read the link. it said i should place the php code. but where should i place it? in the old file? so, should my site have both the old and new file?