You need to create a phpinfo file - PHP has a simple function phpinfo() which does all the hard work so create a file called something like phpinfo.php and paste this into it:
code:
<?php
phpinfo();
?>
and upload it to your server. It should tell you all sorts of information that you need.
However, this information could be used to target you server and so you should delete the file after you find what you want or hide it in a password protected folder.