php script to log the raw data of POST

Write POST data to a file:

file_put_contents('/tmp/postdata.txt', var_export($_POST, true));

You can see the content of POST data inline (not for production) with:

print_r($_POST);

Or if you want to see POST, GET and COOKIE data:

print_r($_REQUEST);

If you need to log, since the client is very limited - try outputting the POST data to a file:

file_put_contents("post.log", print_r($_POST, true));