Password Content Shortcode mod

function cspassword_shortcode($atts, $content = null) {
    if (!isset($_SESSION)) session_start();
    extract(shortcode_atts(array(
        'password' => ''
    ), $atts));

    $csp_text   = get_option('cspassword_text', __("Content with a password", "cs-password"));
    $csp_submit = get_option('cspassword_submit', __("Access", "cs-password"));
    $csp_error  = get_option('cspassword_error', __("Access Denied", "cs-password"));

    $form = '
    <form action="#csp_form" method="post" class="csp_form" id="csp_form">
        '.$csp_text.'
        <input type="password" size="20" name="csp_input">
        <input type="submit" name="csp_submit" value="'.$csp_submit.'">
    </form>
    ';

    if (isset($_POST['csp_submit'])) {
        if ($_POST['csp_input'] == $password AND $password != '') {
            $_SESSION['cclc_full_post_access_' . $post->ID] = true; //added by dbrellis
        }
        else {
            $_SESSION['cclc_full_post_access_' . $post->ID] = false; //added by dbrellis
            return '
            '.$form.'
            <strong>
            '.$csp_error.'
            </strong>
            ';
        }
    }
    if($_SESSION['cclc_full_post_access_' . $post->ID] === true)
        return '<div id="csp_form" style="display:none;"></div>'. do_shortcode($content);
    else return $form;


}
add_shortcode('cspasswordcode', 'cspassword_shortcode');