是否可以在PHP中重载构造函数

e.g in C# you can overload methods using the same method name but what about PHP?

 class Database {
    private $dsn;
    private $host;
    private $user;
    private $password;
    private $enckey;

    function __construct($dbname, $host, $user, $password) {
        $this->dsn = "mysql:dbname=" . $dbname . ';host=' . $host;
        $this->user = $user;
        $this->password = $password;
}
    function __construct($dbname, $host, $user, $password, $enckey) {
        $this->dsn = "mysql:dbname=" . $dbname . ';host=' . $host;
        $this->user = $user;
        $this->password = $password;
        $this->enckey = $enckey;
    }
}

What's the point?

class Database {
    private $dsn;
    private $host;
    private $user;
    private $password;
    private $enckey;

    function __construct($dbname, $host, $user, $password, $enckey = null) {
        $this->dsn = "mysql:dbname=" . $dbname . ';host=' . $host;
        $this->user = $user;
        $this->password = $password;
        $this->enckey = $enckey;
    }
}