A very important thing I should point out is that display_errors SHOULD be disabled for production for security purposes. It's good for a quick look at for errors when testing but you wouldn't want users to see the information that it would put out.
In cPanel x3, go to Select PHP Version > Switch to PHP Settings
Do the following changes to the listed directives/options:
display_errors = Off
log_errors = On
After that press 'save'. Next time when an error/warning/notice/whatever occurs, it won't appear in the browser but it will be logged in 'error.log' files.
Note that these files will be created where the code execution occurs. So if /blah.php gets an error then it would be in /error.log and if /fruit/lemon.php gets an error then it would be /fruit/error.log
You can access these files via file manager or via FTP by opening them as if you're editing code in a file.
What I should also point out is that you should deny access to the file error.log to everyone so that they can't read it unless they have other forms of access such as FTP. I don't know if the file manager would be affected but it's worth trying.