elander, Safari parses PHP all the time, local or otherwise.
Put you do need to install (or at least activate) PHP with the #-removing in httpd.conf
Bull. It READS the code, and presents it as is, but it does not PARSE or EXECUTE. It will parse HTML if it's present in the code, but it will NEVER parse PHP on its own.
You could of course create a Safari plug-in, that would send the PHP code through the php or Zend engine, and then present the result to Safari. Possibly a good idea for testing local files, but I wouldn't recommend it, since it would also parse files received from a misconfigured server.
As for parsing remote code, what are you thinking? A web server correctly configured to handle php-files never sends php code to the browser. It is parsed and executed on the server, and the results (HTML, XHTML, XML, text, images or other document types) are sent to the browser. It never sends any PHP code what so ever. Never.
HyperEdit, on the other hand, can use any PHP engine that you have on your system (e.g. "/usr/bin/php" for the default or "/usr/local/php5" if you've installed PHP 5) to parse and execute the php commands. You can choose which one to use in the settings. The results that come back from the chosen engine are then displayed in a "preview" pane next to the editing pane.
Safari does no such thing. You'll get the same results as if you opened the document in any text editor.