verify_form.php

<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

if (!defined('MOODLE_INTERNAL')) {
    die('Direct access to this script is forbidden.');    // It must be included from a Moodle page.
}

require_once($CFG->dirroot.'/lib/formslib.php');


class verify_form extends moodleform {

    // Define the form.
    public function definition () {
        global $CFG;

        $mform =& $this->_form;
        $mform->addElement('text', 'code', get_string('code', 'simplecertificate'), array('size' => '36'));
        $mform->setType('code', PARAM_ALPHANUMEXT);
        $mform->addRule('code', null, 'required', null, 'client');

        // Add recaptcha if enabeld.
        if ($this->is_recaptcha_enabled()) {
            $mform->addElement('recaptcha', 'recaptcha_element', get_string('security_question', 'auth'));
            $mform->addHelpButton('recaptcha_element', 'recaptcha', 'auth');
            $mform->closeHeaderBefore('recaptcha_element');
        }

        $this->add_action_buttons(false, get_string('verifycertificate', 'simplecertificate'));
    }

    public function validation($data, $files) {
        $errors = parent::validation($data, $files);
        if ($this->is_recaptcha_enabled()) {
            $recaptchaelement = $this->_form->getElement('recaptcha_element');
            if (!empty($this->_form->_submitValues['g-recaptcha-response'])) {
                $response = $this->_form->_submitValues['g-recaptcha-response'];
                if (!$recaptchaelement->verify($response)) {
                    $errors['recaptcha_element'] = get_string('incorrectpleasetryagain', 'auth');
                }
            } else {
                $errors['recaptcha_element'] = get_string('missingrecaptchachallengefield');
            }
        }
        return $errors;
    }

    private function is_recaptcha_enabled() {
        global $CFG;
        return (!empty($CFG->recaptchapublickey) && !empty($CFG->recaptchaprivatekey));
    }

}