<?php
class user {
    private $database = "sqlite:includes/database/users.sqlite";
    private $db;
    private $data = array();


    public function __construct($identifier = NULL) {
        $this->db = new PDO($this->database);

        if (isset($identifier))
            $this->load($identifier);
    }

    public function __get($name) {
        return (isset($this->data[$name]) ? $this->data[$name] : false);
    }

    public function __set($name, $value) {
        $this->data[$name] = $value;
    }

    public function add() {
        if (isset($this->data['id']))
            return false;

        //diese hier brauchen wir unbedingt, sonst kann der user nicht geaddet werden
        $required = array('name', 'email', 'password');
        foreach ($required as $attribute) {
            if (!isset($this->data[$attribute]))
                return false;
        }

        //Encrypt password
        $this->data['password'] = md5($this->data['password']);

        //Prepare SQL query string
        $attributes = '';
        $values = '';
        foreach ($this->data as $attribute => $value) {
            $attributes .= $attribute . ', ';
            $values .= ':' . $attribute . ', ';
        }
        $attributes = trim($attributes, ', ');
        $values = trim($values, ', ');

        $query = 'INSERT INTO users (' . $attributes . ') VALUES (' . $values . ')';
        var_dump($query);

        $db_prep = $this->db->prepare($query);
        foreach ($this->data as $attribute => $value) {
            $db_prep->bindParam(":$attribute", $value);
        }

        //ne gute idee um erfolg zu checken:
        return $db_prep->execute();
    }

    public function load($identifier) {
        if(is_numeric($identifier)) {
            //Get assoc array
            $db_prep = $this->db->prepare("SELECT * FROM users WHERE id = :id");
            $db_prep->bindParam(":id",$identifier);
            $db_prep->execute();
            $this->data = $db_prep->fetch(PDO::FETCH_ASSOC);
            return true;
        }
        else {
            return false;
        }
    }

    //sollte nur nach load ausgeführt werden
    public function save() {
        if (!isset($this->data['id']))
            return false;

        //Encrypt password
        if (isset($this->data['password']))
            $this->data['password'] = md5($this->data['password']);

        //Prepare SQL query string
        $attributes = '';
        foreach ($this->data as $attribute => $value) {
            $attributes .= $attribute . ' = :' . $attribute .  ', ';
        }
        $attributes = trim($attributes, ', ');

        $query = 'UPDATE users SET ' . $attributes . ' WHERE id = ' . $this->data['id'];

        $db_prep = $this->db->prepare($query);
        foreach ($this->data as $attribute => $value) {
            $db_prep->bindParam(':' . $attribute, $value);
        }

        //ne gute idee um erfolg zu checken:
        return $db_prep->execute();

    }
}

?>

// Code to call the class

<?php
error_reporting(E_ALL);
ini_set('display_errors','On');
include("includes/classes.php");
$user = new user();
$user->name = 'arez';
$user->password = 'lalala';
$user->email = 'noone@home.com';
$user->age = '44';
$user->add();

?>

// Error
Fatal error: Call to a member function bindParam() on a non-object in ... on line 52