tszdev

Yes it was.

The variable was assigned at the beginning

public $default_phone_number;

Also the register_settings function is hooked from another class file under admin_init hook like this:

$this->loader->add_action( 'admin_init', $plugin_admin, 'register_setting' );

You need to understand that my problem is not in the declaration of the Var but in getting the option from the db because if I declare the var as equal to 1234 It outputs it.

for instance when I do this:

$this->default_phone_number = 1234;

everything works good but when I do this(as I posted in the original code):

$this->default_phone_number = get_option($this->plugin_name . '_phone');

nothing happens