I have website, that is base on PHP but there is a undefined error occur automatic or may update a PHP latest version

[highadventure43]

I have Hotel website, after updating a PHP version code there is undefined error occur automatic, I don’t know why this error occur and I have a big problem because this error can effect my business. I am also going software company in my local area but still I am facing a problem. I don’t know how to solve this problem. Error on My Website showing in Font Screen: Bolt Error Back to merchant

1. Home Page
2. Room Page
3. Select a Room
4. CheckOut Page
5. Error Page

What I have tried:

I have tried, update my PHP Code or back to old version of PHP Code(Backup file) and Connect with my local area software company, but still facing a problem.

[wake689]

1. We need to see your code.
2. Whereabouts in your code does it echo “something went wrong. Please try again”?
3. Is your site created by WordPress? (the subtitle of your post says “WordPress”)