Set post visibility to password protected

<?php
// http://www.gravityhelp.com/forums/topic/password-protect-a-post-published-by-a-gf-form
// this code goes in your current theme's functions.php file
// change the 349 here to your form ID
add_action('gform_after_submission_349', 'set_post_password', 10, 2);
function set_post_password($entry, $form) {
    // see if the field containing the password has a value
    // change the 6 here to the field in your form where you accepted the post password
    if(check_not_empty($entry[6],1)) {
        $post = get_post($entry['post_id']);
        $post->post_password = $entry[6];
        wp_update_post($post);
    }
}
// props for this function: http://www.php.net/manual/en/function.empty.php#77617
function check_not_empty($s, $include_whitespace = false){
    if ($include_whitespace) {
        // make it so strings containing white space are treated as empty too
        $s = trim($s);
    }
    return (isset($s) && strlen($s)); // var is set and not an empty string ''
}