Random hidden value in Drupal form - drupal-7

Question

I am developing simple guestbook module for one of my customers and as a spam prevention I decided to use an array of simple questions. For this I have to pick random question from the array and set the ID of this question (array element ID) in form so I can check the answer in submit handler. The problem is that the form is regenerated before the submit handler is evaluated so the random value changes.
Shortly: I am getting other value of $form_state['values']['queston_id'] in submit handler function that it is in form. Why is that and how can I change this?
Thanks a lot!
This is my module:
function gb_menu() {
$items = array();
$items['gb'] = array(
'title' => t('Guestbook'),
'description' => t('Guestbook page'),
'page callback' => 'gb_guestbook',
//'page arguments' => array('gb_guestbook'),
'access arguments' => array('view guestbook'),
);
return $items;
}
function gb_guestbook() {
dpm('generating page');
$page = NULL;
$page .= drupal_render(drupal_get_form('gb_guestbook_form'));
$page .= 'list of guestbook messages here';
return $page;
}
function gb_guestbook_form($form, &$form_state) {
$form['name'] = array(
'#type' => 'textfield',
'#title' => t('Name'),
'#description' => t('Please, enter your name.'),
);
$form['message'] = array(
'#type' => 'textarea',
'#cols' => 5,
'#title' => t('Message'),
'#description' => t('Please, enter your message.'),
);
$questions = gb_get_question();
$question_id = rand(0, count($questions)-1);
$question = $questions[$question_id];
$form['question_id'] = array(
'#type' => 'hidden',
'#value' => $question_id,
);
$form['spam'] = array(
'#title' => $question['question'],
'#description' => t('Please, answer the simple question so we know that you are a human.'),
'#type' => 'textfield',
);
$form['submit'] = array(
'#type' => 'submit',
'#value' => t('Submit'),
);
return $form;
}
function gb_guestbook_form_submit($form, &$form_state) {
// spam check
$values = $form_state['values'];
$questions = gb_get_question();
$answers = $questions[$values['question_id']]['answers'];
if (!in_array(strtolower($values['spam']), $answers)) {
drupal_set_message(t('You did not reply the answer correctly. Are you sure it was not typo?'), 'error');
}
else {
drupal_set_message(t('Thanks for the contribution!'), 'status');
// processing input
}
}
function gb_get_question() {
return array(
array (
'question' => t('What is the capital of Slovakia?'),
'answers' => array('bratislava'),
),
array (
'question' => t('What is the name of this band?'),
'answers'=> array('divozel'),
),
array (
'question' => t('What is the biggest town in east part of Slovakia?'),
'answers' => array('košice','kosice'),
),
);
}

Answer 1

You should probably do this check in gb_guestbook_form_VALIDATE instead.

Answer 2

I'd do this in a validation hook. Also another issue in the function gb_guestbook_form_submit
You get the questions but not the answers array and then you are trying to compare them. This could also be the source of your issue, you capture questions but not answers and then compare to the empty array of answers.

Answer 3

Wrap your random question generator in a conditional statement that checks if your question has been defined in the form yet.
$question_id = NULL;
$questions = gb_get_question();
if (!isset($form['question_id'])) {
$question_id = rand(0, count($questions)-1);
}
else {
$question_id = $form['question_id']['#value'];
}
$question = $questions[$question_id];

Answer 4

Not sure why my other answer isn't working for you, but here's another approach. The idea would be to store the question id in $form_state['storage'].
First, correct your form declaration so it passes in $form_state as a reference.
function gb_guestbook_form($form, &$form_state) {
Now check the $form_state['storage'] array for your question id, and set it if you haven't already, before you set the form value question_id.
$questions = gb_get_question();
if (!isset($form_state['storage']['question_id'])) {
$form_state['storage']['question_id'] = array_rand($questions);
}
$form['question_id'] = array(
'#type' => 'hidden',
'#value' => $form_state['storage']['question_id'],
);

Answer 5

Your problem (and mine) is describe here:
http://www.sparklepod.com/myblog/drupal-form-same-form-for-build-and-validation/
In short. On submit the form is rebuild before the validation code is run. For me the solutions in the blog is not working for my Drupal 7 site.
What I have done is added the following line to the forum build:
$form_state['cache'] = true;
That will cache the form and the on _submit I will set it to false.