Organize a form with sections with Admin Page Framework v3. This is an example plugin introduced in the tutrial, Organize a Form with Sections (http://en.michaeluno.jp/admin-page-framework/tutorials-v3/05-organize-a-form-with-sections/).

tutorials-05-create-a-form-with-sections.php

<?php
/* 
    Plugin Name: Admin Page Framework Tutorial 05 - Organize a Form with Sections
    Plugin URI: http://en.michaeluno.jp/admin-page-framework
    Description: Organize a form with sections with Admin Page Framework v3
    Author: Michael Uno
    Author URI: http://michaeluno.jp
    Version: 1.0.1
    Requirements: PHP 5.2.4 or above, WordPress 3.4 or above. Admin Page Framework 3.0.0 or above
*/

include( dirname( __FILE__ ) . '/library/apf/admin-page-framework.php' );

// Extend the class
class APF_CreateForm extends AdminPageFramework {
 
    // Define the setup() method to set how many pages, page titles and icons etc.
    public function setUp() {
       
        // Set the root menu
        $this->setRootMenuPage( 'Settings' );        // specifies to which parent menu to add.
       
        // Add the sub menus and the pages
        $this->addSubMenuItems(   
            array(
                'title'    =>    '5. Adding Forms with Sections',        // the page and menu title
                'page_slug'    =>    'my_second_form'         // the page slug
            )
        );    
        
        $this->addSettingSections(
            'my_second_form',
            array(
                'section_id' => 'my_first_section',
                'title' => 'My First Form Section',
                'description' => 'This section is for text fields.',
            ),
            array(
                'section_id' => 'my_second_section',
                'title' => 'My Second Form Section',
                'description' => 'This section is for selectors.',
            )
        );
        
        // Add form fields
        $this->addSettingFields(
            'my_first_section',
            array(
                'field_id' => 'my_text_field',
                'type' => 'text',
                'title' => 'Text',
                'description' => 'To create multiple fields of the same type, add arrays with numeric keys.',
                array(),    // sub-field
                array(),    // sub-field
            ),
            array(
                'field_id' => 'my_repeatable_text_field',
                'type' => 'text',
                'title' => 'Text',
                'repeatable' => true,
            )
        );
        $this->addSettingFields(
            'my_second_section',
            array(
                'field_id'    =>    'my_checkbox',
                'type'    =>    'checkbox',
                'title'    =>    __( 'Checkbox', 'admin-page-framework-demo' ),
                'label'    =>    __( 'Check me.', 'admin-page-framework-demo' ),
                'default'    =>    false,
            ),            
            array(
                'field_id'    =>    'my_dropdown_list',
                'title'    =>    __( 'Drop-down List', 'admin-page-framework-demo' ),
                'type'    =>    'select',
                'default'    =>    1,    // the index key of the label array below which yields 'Two'.
                'label'    =>    array( 
                    0    =>    'One',        
                    1    =>    'Two',
                    2    =>    'Three',
                ),
            ),    
            array(    
                'field_id'    =>    'radio',
                'title'    =>    __( 'Radio Button', 'admin-page-framework-demo' ),
                'type'    =>    'radio',
                'label'    =>    array( 
                    'a'    =>    'Apple', 
                    'b'    =>    'Banana', 
                    'c'    =>    'Cherry' 
                ),
                'default'    =>    'c',    // yields Cherry; its key is specified.
                'after_label'    =>    '<br />',                
            ),
            array( // Submit button
                'field_id' => 'submit_button_b',
                'type' => 'submit',
                'show_title_column' => false,
            )
        );       
       
    }

    /**
     * @callback        action      do_ + page slug   
     */
    public function do_my_second_form() {  
                   
        // Show the saved option value.
        // The extended class name is used as the option key. This can be changed by passing a custom string to the constructor.
        echo '<h3>Saved Values</h3>';
        echo '<h3>Show as an Array</h4>';
        echo $this->oDebug->getArray( get_option( 'APF_CreateForm' ) );    
        echo '<h3>Retrieve individual field values</h4>';
        echo '<pre>APF_CreateForm[my_first_section][my_text_field][0]: ' . AdminPageFramework::getOption( 'APF_CreateForm', array( 'my_first_section', 'my_text_field', 0 ), 'default' ) . '</pre>';
        echo '<pre>APF_CreateForm[my_second_section][my_dropdown_list]: ' . AdminPageFramework::getOption( 'APF_CreateForm', array( 'my_second_section', 'my_dropdown_list' ), 'default' ) . '</pre>';
        
    }
    
}
 
// Instantiate the class object.
new APF_CreateForm;