Call to a member function on a non-object on WP Plugin Page

Question

I have the following code connecting to the AWS PHP SDK in the form of a Wordpress plugin page. I'm receiving the Call to a member function on a non-object error when trying to use the $MTurk variable in the last function (bz_page_file_path). I've attempted various solutions like $global variables, but have had no luck. I've also confirmed that the code does work if I move the contents of bz_page_file_path into the constructor function (so it appears to be some kind of scoping issue perhaps). What can I do to pass this to the function correctly?

<?php

class BZ_NamePicker {

  // Constructor
  function __construct() {

    require_once dirname(__FILE__) . '/aws-autoloader.php';

    $MTurk = new Aws\MTurk\MTurkClient([
      ...
    ]);

    add_action( 'admin_menu', array( $this, 'bz_add_menu' ));
  }


  /* Action to load admin menu */

  function bz_add_menu() {

    add_menu_page('NamePicker', 'NamePicker', 'manage_options', 'namepicker-dashboard',
      array(__CLASS__, 'bz_page_file_path'),
      'dashicons-sticky','3');
  }

  /* Action to load content on admin webpage */

  function bz_page_file_path() {

    $accountBalance = $MTurk->getAccountBalance([]);
    echo $accountBalance['AvailableBalance'];
  }


}

new BZ_NamePicker();

Answer 1

<?php

class BZ_NamePicker {

  // Constructor
  function __construct() {
     global $MTurk;
    require_once dirname(__FILE__) . '/aws-autoloader.php';

    $MTurk = new Aws\MTurk\MTurkClient([
      ...
    ]);

    add_action( 'admin_menu', array( $this, 'bz_add_menu' ));
  }


  /* Action to load admin menu */

  function bz_add_menu() {

    add_menu_page('NamePicker', 'NamePicker', 'manage_options', 'namepicker-dashboard',
      array(__CLASS__, 'bz_page_file_path'),
      'dashicons-sticky','3');
  }

  /* Action to load content on admin webpage */

  function bz_page_file_path() {
    global $MTurk;
    $accountBalance = $MTurk->getAccountBalance([]);
    echo $accountBalance['AvailableBalance'];
  }


}

new BZ_NamePicker();

you need to call the class in the function you want to access it to, as a global object