When setting up a server phpinfo() is used to determine all is working.
a simple script is made to access this function:

<?php
phpinfo();
?>

saved as phpinfo.php to the server web root.

To troubleshoot the Mysql data base:

<?php
echo mysql_connect ('localhost','username','password');
?>

normally saved as mysql_test.php will test the mysql server connection
and passwords...

These scripts are considered a large security risk on servers, and
should be removed or renamed to a name a hacker would not consider to
hold such a powerful script. Information about your server can lead to a
hackers missuse of your system. Don't install any php script that can
give your information away on a public server. If you must have the
info, name your scripts wisely.