How can I see a varibles value when my plugin runs?

Using the following modifications and adding in die() stopped the script and output whatever the variables value was at that time.

Thanks to @toscho

function cf7pp_after_send_mail( $contact_form ) {

    global $postid;

    $submission = WPCF7_Submission::get_instance();

    if ( $submission ) {
        $posted_data = $submission->get_posted_data();

        $postid = $posted_data['_wpcf7'];

        $enable = get_post_meta( $postid, "_cf7pp_enable", true);
        $email = get_post_meta( $postid, "_cf7pp_email", true);

        $valuepassed = get_post_meta($post_id, "_cf7pp_text_menu_b", true);

        if ($enable == "1") {
           // if ($valuepassed == "1") {
                if ($email == "2") {
                      die( $valuepassed );
                //    include_once ('includes/redirect.php');

                    exit;

                }
           // }
        }
    }
}