basic moodle form

calendar_form.php

<?php
require_once("$CFG->libdir/formslib.php");

class calendar_form extends moodleform {
    public function definition() {
        global $CFG;

        $mform = $this->_form;

        $mform->addElement('text', 'calendarname', get_string('calendarname', 'block_gcal'));
        $mform->setType('calendarname', PARAM_TEXT);
        $mform->setDefault('calendarname', '');

        $mform->addElement('text', 'calendarid', get_string('calendarid', 'block_gcal'));
        $mform->setType('calendarid', PARAM_TEXT);
        $mform->setDefault('calendarid', '');
    }
    function validation($data, $files) {
        return array();
    }
}

mform_calendar_add.php

<?php

require_once(dirname(dirname(__DIR__)).'/config.php');
require_once(__DIR__ . '/calendar_form.php');

require_login();

$context = context_system::instance();
$PAGE->set_context($context);
$url = new moodle_url('/blocks/gcal/add_calendar.php');
$PAGE->set_url($url);

$mform = new calendar_form();
echo $OUTPUT->header();

echo $OUTPUT->heading('mapping', 2);


if ($mform->is_cancelled()) {
} else if ($fromform = $mform->get_data()) {
} else {
    $toform = array();

    $mform->set_data($toform);
    $mform->display();
}

echo $OUTPUT->footer();