ช่วยดูให้หน่อยครับมันบอกว่า Warning: Invalid argument supplied for foreach()

<?

class signup{
    private $username;
    private $password;
    private $passmd5;
    private $email;
    
    private $errors;
    private $token;
    
    public function __construct()
    {
        $this->errors = array();
        
        $this->username = $this->filter($_POST['ruser']);
        $this->password = $this->filter($_POST['rpass']);
        $this->email = $this->filter($_POST['remail']);
        $this->token = $_POST['token'];
        
        $this->passmd5 = md5($this->password);
    }
    
    public function process()
    {
        if($this->valid_token() && $this->valid_data())
            $this->signup();
            
        return count($this->errors) ? 0 : 1;
    }
    
    public function filter($var)
    {
        return preg_replace('/[^a-zA-Z0-5@.]/','',$var);
    }
    
    public function signup()
    {
        mysql_connect('localhost', 'root', '1234') or die (mysql_error());
        mysql_select_db('social') or die (mysql_error());
        
        mysql_query("INSERT INTO account (username,password) VALUES ('($this->username)','($this->passmd5)')");
        
        if(mysql_affected_rows() < 1)
        $this->errors[] = 'Could not process Form';
    }
    
    public function show_errors()
    {
        echo "Errors";
        
        foreach($this->errors as $key=>$value)
        echo $value."<br>";
    }
    
    public function valid_data()
    {
        if(empty($this->username))
            $this->errors[] = 'invail username';
        if(empty($this->password))
            $this->errors[] = 'invail password';
        if(empty($this->email) || !ereg('^[a-zA-Z0-9._-]+@[a-zA-Z0-9._-]\.([a-zA-Z]{2,4})$',$this->email))
            $this->errors[] = 'invail email';
            
            
        return count($this->errors) ? 0 : 1;
    }
    
    public function valid_token()
    {
        if(!isset($_SESSION['token']) || $this->token != $_SESSION['token'])
            $this->errors = 'Incalid subnit';
        
        return count($this->errors) ? 0 : 1;
    }
}

?>