Apache 1.3x/PHP 5.0.3 404 error handler & posted data...

I'm trying to write an error handler in PHP to try to avoid sending the browser a 404 error message. Basically, if someone requests /whatever.html on the server and it doesn't exist, my 404 error handler checks to see if /whatever.php exists, if so, it then includes that file. That part works fine. The part that I'm having trouble with is if /whatever.html happens to be the target of a form POST. With GET requests, the data is available in either $_SERVER['REDIRECT_QUERY_STRING'] or (worst case) $_SERVER['REQUEST_URI']. That's easy enough to parse and turn into $_REQUEST and/or $_GET. However, it seems that POSTed data just vanishes into thin air. $_POST is not set, of course, and I've been trying to read data using file_get_contents('php://input') but nothing is returned... Is this a bug in PHP, Apache, not a bug but an unimplemented feature, security precaution, or what? Am I missing something simple to get the POSTed data? Thank you, Raymond