PHP Fatal error: Uncaught Error: Undefined constant "NAVBAR_TITLE_1"

zc 1.58
php 8.0

My site is upgraded from zc 1.57d. I tried to checkout today and I got the blank page for the last checkout page (before I can submit the order), link is /index.php?main_page=checkout_confirmation

Here is the log file I received:

====
[24-Oct-2022 16:06:16 America/New_York] PHP Fatal error: Uncaught Error: Undefined constant "NAVBAR_TITLE_1" in /includes/modules/pages/checkout_confirmation/header_php.php:168
Stack trace:
#0 /index.php(35): require()
#1 {main}
thrown in /includes/modules/pages/checkout_confirmation/header_php.php on line 168

[24-Oct-2022 16:06:16 America/New_York] Request URI: /index.php?main_page=checkout_confirmation
--> PHP Fatal error: Uncaught Error: Undefined constant "NAVBAR_TITLE_1" in /includes/modules/pages/checkout_confirmation/header_php.php:168
Stack trace:
#0 /index.php(35): require()
#1 {main}
thrown in /includes/modules/pages/checkout_confirmation/header_php.php on line 168.
====

File \includes\modules\pages\checkout_confirmation\header_php.php is unchanged. Here is the code near line 168

require(DIR_WS_MODULES . zen_get_module_directory('require_languages.php'));
$breadcrumb->add(NAVBAR_TITLE_1, zen_href_link(FILENAME_CHECKOUT_SHIPPING, '', 'SSL'));
$breadcrumb->add(NAVBAR_TITLE_2);

// This should be last line of the script:
$zco_notifier->notify('NOTIFY_HEADER_END_CHECKOUT_CONFIRMATION');


I have one page checkout installed but I disabled it for this test.

See if you overrode or modified includes/languages/english/lang.checkout_confirmation.php (in either new or old style).
Without the override, this constant is defined.

Hi @swguy, thanks for pointing me out! I indeed commented out that checkout_confirmation.php/lang.checkout_confirmation.php file. Maybe I read the OPC installation document incorrectly. I added that file back and it worked now! Thanks for your help!!