io farei così
Codice PHP:
include "config.inc.php";

class 
myclass
{
    function 
myclass()
    {
     global 
$config;

     
$this->dbuser $config['sql_user'];
     
$this->dbpass $config['sql_pass'];
     
$this->dbhost $config['sql_host'];
     
$this->dbname $config['sql_name'];
    }

    function 
connect()
    {
     
$this->conn mysql_connect($this->dbhost$this->dbuser,$this->dbpass);
     
mysql_select_db ($this->dbname);
    }
    ...
}

$db = new myclass();