<?php
class test
{
   private $server;
   private $db;
   private $user;
   private $pass;

     function __construct($var1, $var2)
         {

        // do something... validate var1 and var2
        // do $this->var1=$var1; etc


          }

       // other functions
            ...

       public function login($parameter1)

     {
       $this->new=$parameter1;

      my connection and here i would like to use
     $this->server,
     $this->db,
        ...

     }
}

?>

<?php
include 'connections.php';
$class = new test(var1, var2);
$class -> login($parameter1);
?>

<?php

  $server = 'something';
  $db = 'something';
  $user = 'something';
  $pass = 'something';

?>