Basic MainWP one-page extension demo

mainwp-hello-world-extension.php

<?php
/**
 * Plugin Name: MainWP Hello World Extension
 * Plugin URI: https://yourwebsiteurl.com
 * Description: MainWP Hello World Extension is used for the demo.
 * Version: 1.0
 * Author: Your Name
 * Author URI: https://yourwebsiteurl.com
 */

class MainWP_HelloWorld_Extension_Activator {

	protected $mainwpMainActivated = false;
	protected $childEnabled        = false;
	protected $childKey            = false;
	protected $childFile;
	protected $plugin_handle    = 'mainwp-hello-world-extension';
	protected $product_id       = 'MainWP MainWP Hello World Extension';
	protected $software_version = '1.0';

	public function __construct() {
		$this->childFile = __FILE__;

		add_filter( 'mainwp_getextensions', array( &$this, 'get_this_extension' ) );
		$this->mainwpMainActivated = apply_filters( 'mainwp_activated_check', false );

		if ( $this->mainwpMainActivated !== false ) {
			$this->activate_this_plugin();
		} else {
			add_action( 'mainwp_activated', array( &$this, 'activate_this_plugin' ) );
		}
		add_action( 'admin_notices', array( &$this, 'mainwp_error_notice' ) );
	}

	/**
	 * Add your extension to MainWP via the 'mainwp_getextensions' filter.
	 *
	 * @param array $params Array containing the extensions info.
	 *
	 * @return array $params Updated array containing the extensions info.
	 */
	public function get_this_extension( $params ) {
		$params[] = array(
			'plugin'     => __FILE__,
			'api'        => $this->plugin_handle,
			'mainwp'     => false,
			'callback'   => array( &$this, 'settings' ),
			'apiManager' => false,
		);
		return $params;
	}

	/**
	 * Displays the extension page with an adequate header and footer.
	 */
	public function settings() {
		do_action( 'mainwp_pageheader_extensions', __FILE__ );
		?>
		<div class="ui segment">
			<h1><?php esc_html_e( 'Hello World!', 'mainwp' ); ?></h1>
		</div>
		<?php
		do_action( 'mainwp_pagefooter_extensions', __FILE__ );
	}

	/**
	 * Activate the extension API license and initiate the extension.
	 */
	public function activate_this_plugin() {
		$this->mainwpMainActivated = apply_filters( 'mainwp_activated_check', $this->mainwpMainActivated );
		$this->childEnabled        = apply_filters( 'mainwp_extension_enabled_check', __FILE__ );
		$this->childKey            = $this->childEnabled['key'];
	}

	/**
	 * Get the extension key.
	 *
	 * @return string
	 */
	public function get_child_key() {
		return $this->childKey;
	}

	/**
	 * Get the extension file.
	 *
	 * @return string
	 */
	public function get_child_file() {
		return $this->childFile;
	}

	/**
	 * Render the warning notice if the MainWP Dashboard plugin is not activated.
	 */
	public function mainwp_error_notice() {
		global $current_screen;
		if ( $current_screen->parent_base == 'plugins' && $this->mainwpMainActivated == false ) {
			echo '<div class="error"><p>MainWP Hello World Extension ' . __( 'requires <a href="https://mainwp.com/" target="_blank">MainWP Dashboard Plugin</a> to be activated in order to work. Please install and activate <a href="https://mainwp.com/" target="_blank">MainWP Dashboard Plugin</a> first.', 'mainwp' ) . '</p></div>';
		}
	}
}

global $mainWPHelloWorldExtensionActivator;
$mainWPHelloWorldExtensionActivator = new MainWP_HelloWorld_Extension_Activator();