Error: A required parameter (id) was missing when redirect URL in form Moodle - block

Question

Moodle 3, developing a block
I'm getting the following error: 'A required parameter (id) was missing'.
It happens in $mform, only when I'm using the array('id' => $instance->id) in the 'Else if' statement in the redirect($url).
Surprisingly, because when I'm using the same code in a button with a redirect url, the code works correct.
I've tried several things, but nothing helps. What could be the problem?
Here is some code:
$id = required_param('id', PARAM_INT);
$instance = $DB->get_record('block_instances', array('id' => $id), '*', MUST_EXIST);
$context = \context_block::instance($instance->id);
$mform = new newlink();
if ($mform->is_cancelled()) {
$url = new moodle_url('/my');
redirect($url);
} else if ($fromform = $mform->get_data()) {
// data from form
....
$url = new moodle_url('/blocks/name_of_block/links.php', array('id' => $instance->id)); // HERE IS THE PROBLEM
(Note: when I'm using here the block instance id number 123 directly, the redirect is working correct:
$url = new moodle_url('/blocks/name_of_block/links.php?id=123';)
redirect ($url);
} else {
//Set default data (if any)
$mform->set_data($toform);
//displays the form
$mform->display();
}
$url = new moodle_url('/blocks/name_of_block/links.php', array('id' => $instance->id))
echo $OUTPUT->single_button($url, get_string('button:links', 'block_name_of_block')); // THIS IS WORKING CORRECT

Answer 1

Is it when you submit the form rather than the redirect?
In your form do you have:
$mform->addElement('hidden', 'id');
$mform->setType('id', PARAM_INT);
and in the code above do you have:
$toform->id = $id;
$mform->set_data($toform);