WordPress: Tab Layout for Settings Pages

scaffolding.php

<?php
// initialize plugin
if ( function_exists( 'add_action' ) && function_exists( 'register_activation_hook' ) ) {
	add_action( 'plugins_loaded', array( 'tabbed_plugin', 'get_object' ) );
}

class tabbed_plugin
{
	// singleton class variable
	static private $classobj = NULL;
	
	// singleton method
	public static function get_object() {
		if ( NULL === self::$classobj ) {
			self::$classobj = new self;
		}
		return self::$classobj;
	}
				
	private function __construct()
	{
		
	}
}

switch.php

<?php
public function settings_page() {
	switch ( $_REQUEST[ 'tab' ] ) {
		case 'tab2':
			$tab = 'tab2';
			break;
		case 'tab3':
			$tab = 'tab3';
			break;		
		default:
			$tab = 'tab1';
			break;
	}
	?>
	<!-- ... -->

		<div class="metabox-holder has-right-sidebar">
			<?php
			$this->settings_page_sidebar();

			switch ( $tab ) {
				case 'tab1':
					$this->settings_page_tab1();
					break;
				case 'tab2':
					$this->settings_page_tab2();
					break;					
				case 'tab3':
					$this->settings_page_tab3();
					break;
			}
			?>
		</div> <!-- .metabox-holder -->
	<!-- ... -->
	<?php
}

tabbed_plugin.php

<?php
/*
Plugin Name: Tabbed Plugin
Plugin URI: 
Description: 
Version: 1.0
Author: Eric Teubert
Author URI: ericteubert@googlemail.com
License: MIT
*/

// initialize plugin
if ( function_exists( 'add_action' ) && function_exists( 'register_activation_hook' ) ) {
	add_action( 'plugins_loaded', array( 'tabbed_plugin', 'get_object' ) );
}

class tabbed_plugin
{
	// singleton class variable
	static private $classobj = NULL;
	
	// internationalization textdomain
	public static $textdomain = 'tabbed_plugin';
	
	private $settings_page_handle = 'tabbed_plugin_options_handle';
	
	// singleton method
	public static function get_object() {
		if ( NULL === self::$classobj ) {
			self::$classobj = new self;
		}
		return self::$classobj;
	}
				
	private function __construct()
	{
		add_action( 'admin_menu', array( $this, 'add_menu_entry' ) );
	}
	
	public function add_menu_entry() {
		add_submenu_page( 'options-general.php', 'Tabbed Plugin', 'Tabbed Plugin', 'manage_options', $this->settings_page_handle, array( $this, 'settings_page' ) );
	}
	
	public function settings_page() {
		$tab = ( $_REQUEST[ 'tab' ] == 'tab2' ) ? 'tab2' : 'tab1';
		?>
		<div class="wrap">
			<div id="icon-options-general" class="icon32"></div>
			<h2 class="nav-tab-wrapper">
				<a href="<?php echo admin_url( 'options-general.php?page=' . $this->settings_page_handle ) ?>" class="nav-tab <?php echo ( $tab == 'tab1' ) ? 'nav-tab-active' : '' ?>">
					<?php echo __( 'Tab1', self::$textdomain ) ?>
				</a>
				<a href="<?php echo admin_url( 'options-general.php?page=' . $this->settings_page_handle . '&tab=tab2' ) ?>" class="nav-tab <?php echo ( $tab == 'tab2' ) ? 'nav-tab-active' : '' ?>">
					<?php echo __( 'Tab2', self::$textdomain ) ?>
				</a>
			</h2>

			<div class="metabox-holder has-right-sidebar">
				<?php
				$this->settings_page_sidebar();

				if ( $tab == 'tab1' ) {
					$this->settings_page_tab1();
				} else {
					$this->settings_page_tab2();
				}
				?>
			</div> <!-- .metabox-holder -->
		</div> <!-- .wrap -->
		<?php
	}
	
	private function settings_page_sidebar() {
		# see http://www.satoripress.com/2011/10/wordpress/plugin-development/clean-2-column-page-layout-for-plugins-70/
		?>
		<div class="inner-sidebar">

			<div class="postbox">
				<h3><span>Sidebar Box</span></h3>
				<div class="inside">
					<p>Hi, I'm a persistent sidebar.<br/>Visible on all Tabs!</p>
				</div>
			</div>

		</div> <!-- .inner-sidebar -->
		<?php
	}
	
	private function settings_page_tab1() {
		?>
		<div id="post-body">
			<div id="post-body-content">

				<div class="postbox">
					<h3><span>Metabox in Tab1</span></h3>
					<div class="inside">
						<p>Hi, I'm content visible in the first Tab!</p>
					</div> <!-- .inside -->
				</div>

			</div> <!-- #post-body-content -->
		</div> <!-- #post-body -->	
		<?php
	}
	
	private function settings_page_tab2() {
		?>
		<div id="post-body">
			<div id="post-body-content">

				<div class="postbox">
					<h3><span>Metabox in Tab 2</span></h3>
					<div class="inside">
						<p>Hi, I'm content visible in the second Tab!</p>
					</div> <!-- .inside -->
				</div>

			</div> <!-- #post-body-content -->
		</div> <!-- #post-body -->	
		<?php
	}
}

nice one keep up

defining text domain as a variable self::$textdomain will make the gettext programs like PO Edit or loco translate unable to translate this keyword because these programs don't parse PHP, but they parse the code as a text