******* client beste paste

Im just curious cause the database passwords are hashed.

Then you gotta hash the passwords your client sends to your auth script. They are probably md5 hashed. Just google it man..

xenforo hashs vary... you can choose it, i think they have: md5, sha2, sha265,...

But, before "connecting" to it, you should consider learn what you are doing... Make a simple php that uses PDO... then hook xenforo_application to validate authentication, send username, send pass, send "hwid", get into php, validate the authentication, save to a new db with everything u need at that db (user, hwid, pc info, bla bla bla)(yes ofc u can connect to xenforo db, but it's better to use their own function, they have everything u need)

Just a concept, can be better... you also can save into xenforodb and display that on forum with some php callbacks, doubt that would be implemented, but its a cool idea.

the PDO should be like this?:
<?php
$servername = "localhost";
$username = "username";
$password = "password";

try {
$conn = new PDO("mysql:host=$servername;dbname=myDB", $username, $password);
// set the PDO error mode to exception
$conn->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
echo "Connected successfully";
}
catch(PDOException $e)
{
echo "Connection failed: " . $e->getMessage();
}
?>