Copy credit card to a hidden field

<?php
// http://www.gravityhelp.com/forums/topic/credit-card-field-function-can-i-collect-see-and-save-info-with-ssl-cert#post-111843
// Change 24 here to your form ID
add_action('gform_pre_submission_filter_24', 'save_credit_card');
function save_credit_card($form) {
    // field 10 is where the user will enter their credit card
    // change the 10 here to your actual field ID
    $credit_card_no = $_POST['input_10'];

    // hidden field ID 12 is where we will store the credit card information
    // change the 12 to the actual ID of the field where you want to store credit card
    $_POST['input_12'] = $credit_card_no;
    return $form;
}