Nginx not logging PHP errors
You have to add the following to your php-fpm pool configurations:
catch_workers_output = 1
You have to add this line to each defined pool!
I had a similar issue.
I tried deploy phpMyAdmin with php-fpm 7.0 and nginx on CentOS7. Nginx showed me 500.html but there was not errors in any log file. I did all of this
catch_workers_output = 1
and
display_errors = On
Either nginx log or php-fpm log did not contained any error string.
And when I commented this line in nginx.conf I was able to see in browser page things that was wrong.
# error_page 500 502 503 504 /50x.html;
# location = /50x.html {
# }
That was what helped me understand troubles.
php-fpm
throws everything in /var/log/php5-fpm.log
or similar.