这些是第一行：

define('SIMPLE_DB_SERVER','MysqLserver.net');
define('SIMPLE_DB_NamE','mydbname');
define('SIMPLE_DB_USERNAME','myusername');
define('SIMPLE_DB_PASSWORD','mypassword');
class ASimpleMysqLDB {
    public function __construct($server,$database,$username,$password){

        $this->conn = MysqL_connect($server,$password);
        $this->db = MysqL_select_db($database,$this->conn);
    }
[...]

我想知道在类之外定义哪些常量的具体原因,而不是使用构造函数 – 例如：

public function __construct(){
    $this->conn = MysqL_connect('localhost','username','password');
    $this->db = MysqL_select_db('database',$this->conn);
}

要么：

public function __construct($which_db){
        if($which_db=='Firstdb'){
            $server='localhost';
            $username='user1';
            $password='pass1';
            $database='db1';
        }elseif($which_db=='otherdb'){
            $server='localhost';
            $username='user2';
            $password='pass2';
            $database='db2';
        }

    $this->conn = MysqL_connect($server,$password);
    $this->db = MysqL_select_db($database,$this->conn);

}

或者使用开关或其他任何东西.

这两种方法有什么区别？你会推荐哪个？非常感谢 ：-)