Question

I have a problem with that header.
When the page is processed I will only exit();

if($validate=='true') {
        $_SESSION['nome'] = $nome;
        $_SESSION['cognome'] = $cognome;
        $_SESSION['email'] = $email;
        $_SESSION['telefono'] = $telefono;
        $_SESSION['cellulare'] = $cellulare;
        $_SESSION['password'] = $password;
        $_SESSION['societa'] = $societa;
        $_SESSION['pi'] = $pi;
        $_SESSION['cf'] = $tax;
        $controllor = md5(uniqid(rand(), TRUE));

        ob_start();
             header("Location: index.php?nav=8&controllor=".$controllor);
        ob_end_flush();
        exit();


    }

All variables above are filled correctly and $validate is equal to ‘true’.

Answer 1

Firstly, using output buffering to avoid writing proper code should be avoided; it could potentially have saved you from this.

Secondly, the way you are using output buffering to avoid header error messages, is wrong.
Output buffering should be started as the first thing.

With no error messages or more code to work out your problem, an obvious suggestion would be to remove the output buffering, move the functionality with the header function() to a point before any output to the browser is made.