Woocommerce cart items not working in function.php

Question

In Woocommerce I have a simple function which return cart items and when I call this function in function.php I have an error .

<?php 
class Theme { 
 public static $version;
 function __construct() { 
  $theme = wp_get_theme();
  self::$version = $theme['Version'];   
  $this->cart_items(); 
  } 
 function cart_items(){ 
   var_dump(get_users()); 
 } 
new Theme();

And I have this error:

Fatal error: Uncaught Error: Call to a member function get_cart_contents() on null

Answer 1

Please add this below code
<?php 
class Theme { 
 public static $version;
 function __construct() { 
  $theme = wp_get_theme();
  self::$version = $theme['Version'];   
  $this->cart_items(); 
  } 
 function cart_items(){ 
   var_dump(get_users()); 
 } 
}
new Theme();