[php] $_POST vs. $_SERVER['REQUEST_METHOD'] == 'POST'

If your application needs to react on request of type post, use this:

if(strtoupper($_SERVER['REQUEST_METHOD']) === 'POST') { // if form submitted with post method
    // validate request, 
    // manage post request differently, 
    // log or don't log request,
    // redirect to avoid resubmition on F5 etc
}

If your application needs to react on any data received through post request, use this:

if(!empty($_POST)) {  // if received any post data
   // process $_POST values, 
   // save data to DB,
   // ... 
}

if(!empty($_FILES)) { // if received any "post" files
   // validate uploaded FILES
   // move to uploaded dir
   // ...
}

It is implementation specific, but you a going to use both, + $_FILES superglobal.