Riportare classe in un file di testo

[techno]

Scusami ti disturbo per ancora un po, io ho fatto questo:

$string = '<?php

class database{

    public $dbhost = "'.$host_database.'";
    public $namedb = "'.$name_database.'";
    public $dbpsw = "'.$password_database.'";

    private $host;
    private $root;
    private $password;
    private $dbname;
    private $dbconn;
    private $result;

    function __construct($dbhost, $namedb, $dbpsw) {
        $this->host = $dbhost;
        $this->root = "root";
        $this->password = $dbpsw;
        $this->dbname = $namedb;
    }
...
}
?>';

Le variabili le passa le scrive sul file ma mi da questo errore:
Fatal error: Uncaught ArgumentCountError: Too few arguments to function database::__construct(), 0 passed in...


Questo è il file creato:

class database{
    public $dbhost = "localhost";
    public $namedb = "auditwork";
    public $dbpsw = "";
    private $host;
    private $root;
    private $password;
    private $dbname;
    private $dbconn;
    private $result;
    function __construct($dbhost, $namedb, $dbpsw) {
        $this->host = $dbhost;
        $this->root = "root";
        $this->password = $dbpsw;
        $this->dbname = $namedb;
    } 

come vedi il contenuto delle variabili ci sono