WordPress - How to create a Setting Page with options.php

<?php

add_action('admin_init', function () {
    // register a new setting for "wporg" page
    register_setting('wporg', 'wporg_options');

    // register a new section in the "wporg" page
    add_settings_section(
        'wporg_section_developers',
        __('The Matrix has you.', 'wporg'),
        'wporg_section_developers_cb',
        'wporg'
    );

    // register a new field in the "wporg_section_developers" section, inside the "wporg" page
    add_settings_field(
        'wporg_field_pill', // as of WP 4.6 this value is used only internally
        // use $args' label_for to populate the id inside the callback
        __('Pill', 'wporg'),
        'wporg_field_pill_cb',
        'wporg',
        'wporg_section_developers',
        [
            'label_for' => 'wporg_field_pill',
            'class' => 'wporg_row',
            'wporg_custom_data' => 'custom',
        ]
    );

    add_settings_field(
        'wporg_field_pill_2', // as of WP 4.6 this value is used only internally
        // use $args' label_for to populate the id inside the callback
        __('Pill', 'wporg'),
        'wporg_field_pill_cb',
        'wporg',
        'wporg_section_developers',
        [
            'label_for' => 'wporg_field_pill_2',
            'class' => 'wporg_row',
            'wporg_custom_data' => 'custom',
        ]
    );
});

/**
 * custom option and settings:
 * callback functions
 */

// developers section cb

// section callbacks can accept an $args parameter, which is an array.
// $args have the following keys defined: title, id, callback.
// the values are defined at the add_settings_section() function.
function wporg_section_developers_cb($args)
{
    ?>
 	<p id="<?php echo esc_attr($args['id']); ?>">
 		<?php esc_html_e('Follow the white rabbit.', 'wporg');?>
 	</p>
 <?php
}

// pill field cb

// field callbacks can accept an $args parameter, which is an array.
// $args is defined at the add_settings_field() function.
// wordpress has magic interaction with the following keys: label_for, class.
// the "label_for" key value is used for the "for" attribute of the <label>.
// the "class" key value is used for the "class" attribute of the <tr> containing the field.
// you can add custom key value pairs to be used inside your callbacks.
function wporg_field_pill_cb($args)
{
    // get the value of the setting we've registered with register_setting()
    $options = get_option('wporg_options');
    // output the field
    ?>
 <select id="<?php echo esc_attr($args['label_for']); ?>"
 data-custom="<?php echo esc_attr($args['wporg_custom_data']); ?>"
 name="wporg_options[<?php echo esc_attr($args['label_for']); ?>]"
 >
 <option value="red" <?php echo isset($options[$args['label_for']]) ? (selected($options[$args['label_for']], 'red', false)) : (''); ?>>
 <?php esc_html_e('red pill', 'wporg');?>
 </option>
 <option value="blue" <?php echo isset($options[$args['label_for']]) ? (selected($options[$args['label_for']], 'blue', false)) : (''); ?>>
 <?php esc_html_e('blue pill', 'wporg');?>
 </option>
 </select>
 <p class="description">
 <?php esc_html_e('You take the blue pill and the story ends. You wake in your bed and you believe whatever you want to believe.', 'wporg');?>
 </p>
 <p class="description">
 <?php esc_html_e('You take the red pill and you stay in Wonderland and I show you how deep the rabbit-hole goes.', 'wporg');?>
 </p>
 <?php
}

/**
 * top level menu
 */

/**
 * register our wporg_options_page to the admin_menu action hook
 */
add_action('admin_menu', function () {
    // add top level menu page
    add_menu_page(
        'WPOrg',
        'WPOrg Options',
        'manage_options',
        'wporg',
        'wporg_options_page_html'
    );
});

/**
 * top level menu:
 * callback functions
 */
function wporg_options_page_html()
{
    // check user capabilities
    if (!current_user_can('manage_options')) {
        return;
    }

    // add error/update messages

    // check if the user have submitted the settings
    // wordpress will add the "settings-updated" $_GET parameter to the url
    if (isset($_GET['settings-updated'])) {
        // add settings saved message with the class of "updated"
        add_settings_error('wporg_messages', 'wporg_message', __('Settings Saved', 'wporg'), 'updated');
    }

    // show error/update messages
    settings_errors('wporg_messages');
    ?>
 <div class="wrap">
 <h1><?php echo esc_html(get_admin_page_title()); ?></h1>
 <form action="options.php" method="post">
 <?php
// output security fields for the registered setting "wporg"
    settings_fields('wporg');
    // output setting sections and their fields
    // (sections are registered for "wporg", each field is registered to a specific section)
    do_settings_sections('wporg');
    // output save settings button
    submit_button('Save Settings');
    ?>
 </form>
 </div>
 <?php
}