running php with .html files?

Hi All, I'm sure I saw a posting on this subject a month ago so please excuse me for not paying attention the first time ;-| I have a php script that I wish to execute but I want to put it in index.html (not index.php) I know there is a solution involving configuration files in either the directory wher the file is held or specifically for the server. (Unfortunately I don't have access to the conf files for the server because I'm currently using a shared serever from an ISP). Any help is greatly appreciated. Even pointers in the right direction would be useful. TIA Henry