classes/admin/setting_button.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/>.

/**
 * Admin config settings page
 *
 * @package    auth_saml2
 * @copyright  Brendan Heywood <brendan@catalyst-au.net>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */

namespace auth_saml2\admin;
use admin_setting_heading;
use html_writer;

defined('MOODLE_INTERNAL') || die();

require_once($CFG->libdir . '/moodlelib.php');

/**
 * Settings for label type admin setting.
 *
 * @package    auth_saml2
 * @copyright  Matt Porritt <mattp@catalyst-au.net>
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
class setting_button extends admin_setting_heading {
    /** @var string Button label */
    protected $label;
    /** @var string Button href */
    protected $href;

    /**
     * A button element
     *
     * @param string $name        unique ascii name.
     * @param string $visiblename heading
     * @param string $description description of what the button does
     * @param string $label       what is written on the button
     * @param string $href        the URL directed to on click
     */
    public function __construct($name, $visiblename, $description, $label, $href) {
        $this->nosave = true;
        $this->label = $label;
        $this->href = $href;
        parent::__construct($name, $visiblename, $description, '');
    }

    /**
     * Returns an HTML string
     * @param mixed $data
     * @param string $query
     * @return string Returns an HTML string
     */
    public function output_html($data, $query = '') {
        if (moodle_major_version() < '3.3') {
            $params = [
                'type'    => 'button',
                'value'   => $this->label,
                'onclick' => 'location.href="' . $this->href . '"',
            ];

            $content = html_writer::empty_tag('input', $params);
            $element = html_writer::div($content, 'form-text defaultsnext');
        } else {
            global $OUTPUT;
            $context = (object)[
                'label'    => $this->label,
                'href'     => $this->href,
                'forceltr' => $this->get_force_ltr(),
            ];

            $element = $OUTPUT->render_from_template('auth_saml2/setting_configbutton', $context);
        }

        return format_admin_setting($this, $this->visiblename, $element, $this->description);
    }
}
