[Not a bug] PHP Warning: Illegal string offset on PHP 7.2

PHP 7.2.7
Website throwing a 500 internal error on checkout and admin can not edit orders, but I can do everything else???

[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Illegal string offset 'cPath' in /home4/XXXXX/public_html/zencart/includes/classes/navigation_history.php on line 40
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Illegal string offset 'products_id' in /home4/XXXXX/public_html/zencart/includes/classes/navigation_history.php on line 40
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' (this will throw an Error in a future version of PHP) in /home4/XXXXX/public_html/zencart/includes/functions/html_output.php on line 319
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: A non-numeric value encountered in /home4/XXXXX/public_html/zencart/includes/classes/categories_ul_generator.php on line 58
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant MODULE_ORDER_TOTAL_GV_STATUS - assumed 'MODULE_ORDER_TOTAL_GV_STATUS' (this will throw an Error in a future version of PHP) in /home4/XXXXX/public_html/zencart/includes/templates/westminster_new/templates/tpl_modules_mobile_categories_tabs.php on line 71
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant MODULE_ORDER_TOTAL_GV_STATUS - assumed 'MODULE_ORDER_TOTAL_GV_STATUS' (this will throw an Error in a future version of PHP) in /home4/XXXXXX/public_html/zencart/includes/modules/sideboxes/westminster_new/information.php on line 48
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' (this will throw an Error in a future version of PHP) in /home4/XXXXXXX/public_html/zencart/includes/functions/html_output.php on line 319
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' (this will throw an Error in a future version of PHP) in /home4/XXXXXXX/public_html/zencart/includes/functions/html_output.php on line 319
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant LARGE_IMAGE_WIDTH - assumed 'LARGE_IMAGE_WIDTH' (this will throw an Error in a future version of PHP) in /home4/XXXXXXXX/public_html/zencart/includes/templates/westminster_new/templates/tpl_modules_main_product_image.php on line 25
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant LARGE_IMAGE_HEIGHT - assumed 'LARGE_IMAGE_HEIGHT' (this will throw an Error in a future version of PHP) in /home4/XXXXXXXX/public_html/zencart/includes/templates/westminster_new/templates/tpl_modules_main_product_image.php on line 25
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' (this will throw an Error in a future version of PHP) in /home4/XXXXXXXX/public_html/zencart/includes/functions/html_output.php on line 319
[09-Sep-2019 06:04:25 America/Chicago] PHP Warning: Use of undefined constant CSS_BUTTON_POPUPS_IS_ARRAY - assumed 'CSS_BUTTON_POPUPS_IS_ARRAY' (this will throw an Error in a future version of PHP) in /home4/XXXXXXXX/public_html/zencart/includes/functions/html_output.php on line 319

Anything that can be done, just noticed this last week. If not, I will nuke and upgrade to 1.5.6

1. All those PHP Warnings would not trigger a 500 Error. Something else is causing the Fatal error which triggers the 500 response.

2. All those are related to incompatibility with PHP 7.2 ... which your 1.5.4 release is not compatible with. Neither are your un-upgraded plugins/addons/templates/customizations.

Thanks. Looks like I'm upgrading.

When performing the upgrade, suggest using: http://www.zen-cart.com/entry.php?3-How-do-I-rebuild-my-site-on-the-new-version-instead-of-upgrading