[WordPress] Demonstrating the SRP using WordPress submenu items and pages.

00-a-submenu-item.php

<?php

class Dashboard {

	public function init() {
		add_action( 'admin_menu', array( $this, 'add_options_page' ) );
	}
	
	public function add_options_page() {

		add_options_page(
			'New Admin Page',
			'New Admin Page',
			'manage_options',
			'new-admin-page',
			array( $this, 'render' )
		);
	}
	
	public function render() {
		echo "Hello world!";
	}
	
}

01-submenu.php

<?php

class Submenu {

	private $options_page;

	public function __construct( $options_page ) {
		$this->options_page = $options_page;
	}
	
	public function init() {

		add_action(
			'admin_menu',
			array( $this->options_page, 'display' )
		);

	}
}

02-options-page.php

<?php

class Options_Page {

	private $options;

	public function __construct() {
    		$this->options = get_option( 'acme-options-key' );
	}

	public function display() {

		add_options_page(
			'Acme Page Title',
			'Submenu Item Title',
			'manage_options',
			'acme-options-page',
			array( $this, 'render' )
		);

	}

	public function render() {
		/**
		 * This is where you can display any of the content for the page.
		 * Some will write inline HTML, some will use an `echo` statement,
		 * and others will use an `include_once` to another file. 
		 */
	}
}

03-create-submenu-page.php

<?php

add_action( 'plugins_loaded', 'acme_create_submenu_page' );
function acme_create_submenu_page() {
  $submenu = new Submenu( new Options_Page() );
}