Got this working the other day in a single-file php plugin which only consisted of functions.

Now I am trying it out with the WordPress Plugin Boilerplate which is an OOP approach with a lot of different classes.

In short, I am looking at two different classes/files

includes/class-ebay-keyword-suggest.php and admin/class-ebay-keyword-suggest-admin.php

The first being the core plugin class, and the latter being the admin-specific functionality.

First, class-ebay-keyword-suggest.php __construct()'s

public function __construct() {
    if ( defined( 'EBAY_KEYWORD_SUGGEST_VERSION' ) ) {
        $this->version = EBAY_KEYWORD_SUGGEST_VERSION;
    } else {
        $this->version = '1.0.0';
    }
    $this->plugin_name = 'ebay-keyword-suggest';

    $this->load_dependencies();
    $this->set_locale();
    $this->define_admin_hooks();
    $this->define_public_hooks();
    $this->register_admin_menu();
}

load_dependencies loads the class-ebay-keyword-suggest-admin.php file, among others.

ends with defining $this->loader as such:

$this->loader = new Ebay_Keyword_Suggest_Loader();

define_admin_hooks loads up my scripts and stylesheets

private function define_admin_hooks() {
    $plugin_admin = new Ebay_Keyword_Suggest_Admin( $this->get_plugin_name(), $this->get_version() );
    $this->loader->add_action( 'admin_enqueue_scripts', $plugin_admin, 'enqueue_styles' );
    $this->loader->add_action( 'admin_enqueue_scripts', $plugin_admin, 'enqueue_scripts' );
}

Proceeded by register_admin_menu:

private function register_admin_menu() {
    $plugin_admin = new Ebay_Keyword_Suggest_Admin( $this->get_plugin_name(), $this->get_version() );
    add_action( 'admin_init', array( $plugin_admin, 'ebay_keyword_suggest_settings_init' ) );
    add_action( 'admin_menu', array( $plugin_admin, 'ebay_keyword_suggest_add_admin_menu' ) );
    add_action( 'admin_enqueue_scripts', array( $plugin_admin, 'enqueue_localize' ) );
}

ebay_keyword_suggest_settings_init is where I am registering the option/setting ebay_keyword_suggest_settings with callbacks

public function ebay_keyword_suggest_settings_init() { 

register_setting( 'pluginPage', 'pluginPage', array($this, 'ebay_keyword_suggest_settings'));

add_settings_section(
    'ebay_keyword_suggest_pluginPage_section', 
    __( 'Your section description', 'https://bruman.dev' ),
    array($this, 'ebay_keyword_suggest_settings_section_callback'),
    'pluginPage'
);

add_settings_field( 
    'ebay_keyword_suggest_checkbox_field_0', 
    __( 'Settings field description', 'https://bruman.dev' ), 
    array($this, 'ebay_keyword_suggest_checkbox_field_0_render'),
    'pluginPage', 
    'ebay_keyword_suggest_pluginPage_section' 
);
}

Next in line in the add_action functions of register_admin_menu via ebay_keyword_suggest_add_admin_menu

public function ebay_keyword_suggest_add_admin_menu() {
    add_options_page( 'eBay Keyword Suggest', 'eBay Keyword Suggest', 'manage_options', 'ebay_keyword_suggest',  array($this, 'ebay_keyword_suggest_options_page') );
}

Then we get to this line:

add_action( 'admin_enqueue_scripts', array( $plugin_admin, 'enqueue_localize' ) );

public function enqueue_localize( $hook ) {
    $getoption = get_option( 'ebay_keyword_suggest_settings' );
    $enabled = $getoption['ebay_keyword_suggest_checkbox_field_0'];
    wp_localize_script( $this->plugin_name, 'ekw_script_vars', array( 'enabled' => __($enabled) ) );
}

As you can see the first instance of get_option is initiated here under the variable $getoption... doing a var_dump always returns false (and of course wp_localize_script does not work properly as it is not getting the proper option variable.

Getting this working in a single php file was very easy with a combination of add_action's above the functions and a simple initiation of register_setting( 'pluginPage', 'title_char_count_settings' ); followed by retrieving the setting with just simple get_option( 'title_char_count_settings' );

This OOP approach is a lot more tricky... I have to be close I'm thinking.. where is the hiccup in this?