is_file keeps returning false

I'm trying to connect to database but when it's trying to check the file, it keeps returning error.

<?php

class Database
{
    private $host;
    private $user;
    private $password;
    private $database;

    function __construct($filename){

        if(is_file($filename)) include '../include/connect.php';
        else throw new exception("Error!"); //<--- keeps returning "Error!"

        $this->host=$host;
        $this->user=$user;
        $this->password=$password;
        $this->database=$database;
    }

Here is my connect.php:

    <?php
$host = "localhost";
$user = "root";
$password= "";
$database= "audiologiska_kliniken";