setcookie doesn't work after form submission [closed]

Question

I can set cookies using setcookie function. If I submit a form, then setcookie doesn't work. The function is called but I don't get any cookie.

<?php
/*
Plugin Name: DoSomething
Version: 0.1
*/

class DoSomething
{
    public function displayForm()
    {
        if (!isset($_COOKIE['do-something'])) {
            require_once('form.php');
        }
    }

    public function formSubmission()
    {
        if (isset($_POST) && !empty($_POST)) {
            // do something here...
        }
    }

    public function skip()
    {
        if (isset($_GET['do-something'])) {
            self::cookies();
        }
    }

    public function cookies()
    {
        $url = parse_url(get_bloginfo('url'));
        setcookie(
            'do-something',
            TRUE,
            3600,
            $url['path'],
            $url['host']
        );
    }
}

add_action('init', array('DoSomething', 'skip'));
add_action('init', array('DoSomething', 'formSubmission'), 1);
add_action('wp_loaded', array('DoSomething', 'displayForm'));
?>

I don't know what to do. Can you help me, please? Thanks.

UPDATE: I've used $_SESSION instead and now it's working. Pretty weird :S Thanks.