Using stand-alone PHP scripts with Drupal

Hi, I know this is probably more a Drupal question, but I'm guessing some here have probably had to deal with this. I've written some PHP code which works just fine on its own. Now someone wants to include it in their Drupal site, with the regular headers and footers for their site surrounding the output from my scripts. Is there an easy way to include the PHP in a page on their site? Not sure which version of Drupal they're running, trying to find out. Geoff.