[Admin]

I'd just save this file as newest.php or something like that:

PHP Code:

<?php

error_reporting(7);

require("./global.php");

$getnewestusers=$DB_site->query_first("SELECT userid,username FROM user ORDER BY joindate DESC LIMIT 1");
$newusername=$getnewestusers['username'];
$newuserid=$getnewestusers['userid'];

echo "<a href=member.php?s=&action=getinfo&userid=$newuserid>$newusername</a>";

?>

But anyway, your problem is that:
a) you're missing the 's in your query:

$getnewestusers=$DB_site->query_first("SELECT userid,username FROM user WHERE userid='$numbersmembers[max]'");

and b) where are you getting $numbersmembers[max] from? You need to use another query to get it:

PHP Code:

$numbersmembers=$DB_site->query_first('SELECT MAX(userid) AS max FROM user'); 


So your file should look like this:

PHP Code:

<?php

require("admin/config.php");

$dbclassname="admin/db_$dbservertype.php";
require($dbclassname);

$DB_site=new DB_Sql_vb;

$DB_site->appname="VBulletin";
$DB_site->appshortname="VBulletin (forum)";
$DB_site->database=$dbname;
$DB_site->server=$servername;
$DB_site->user=$dbusername;
$DB_site->password=$dbpassword;

$DB_site->connect();

$numbersmembers=$DB_site->query_first('SELECT MAX(userid) AS max FROM user');
$getnewestusers=$DB_site->query_first("SELECT userid,username FROM user WHERE userid='$numbersmembers[max]'");
$newusername=$getnewestusers['username'];
$newuserid=$getnewestusers['userid'];


echo "<a href=member.php?s=&action=getinfo&userid=$newuserid>$newusername</a>";

?>