Mysql – PHP cannot connect to MySQL

How are you calling mysql_query()? I notice that you don't save the connection handle from the mysql_connect() call. It looks to me like the failing mysql_query() call is not using the connection you're making.

I recommend that you revise your code to do something like this:

function connect_db() {
    // Reads the config file
    include('system_config.php');

    if ($SYSTEM_DB_HOST == "") {
        return false;
    }

    $dbhandle = mysql_connect($SYSTEM_DB_HOST, $SYSTEM_DB_USER, $SYSTEM_DB_PASS);
    if ($dbhandle) {
        @mysql_select_db($SYSTEM_DB, $dbhandle);

        return $dbhandle;
    } else {
        return false;
    }
}

// ... invoke like this:
$dbhanle = connect_db();
if (!$dbhandle) {
    // handle failed DB connection
}

// later, whenever you need to run queries:
$result = mysql_query($querysql, $dbhandle);

This will ensure that the connection you make with mysql_connect is in fact the one that is used for the query. See if that changes anything; even if it doesn't, personally I think it's good practice to explicitly tell MySQL which DB connection you want to use.

You need to simply remove the anonymous user.

In the future, running /usr/bin/mysql_secure_installation (Location in RPM Installation) will prompt you to remove these anonymous users.

By default, a MySQL installation has an anonymous user, allowing anyone to log into MySQL without having to have a user account created for them. This is intended only for testing, and to make the installation go a bit smoother. You should remove them before moving into a production environment.

Remove anonymous users? [Y/n] y ... Success!