New nginx makes PHP website return blank page

Recently, I upgraded Nginx in this server and after some days, I discovered that one of my PHP websites (for internal use) was not working! It just returned completely blank page (no text or HTML source), even with the script containing only phpinfo().

At first, I didn't know that it was caused by Nginx, or it is because of upgrading Nginx. I tried to look in to various log files, from Nginx's to php5-fpm but did not see anything. I configured PHP to always display error, still no help. Searching around, I found that someones in Internet also get this phenomenon, after upgrading Nginx. Some suggests to change Nginx's virtual host configuration (the files in /etc/nginx/sites-available/). So I understand that new Nginx may bring changes that old configuration file will not be compatible!

But, then there is a question: How do I know how the configuration should be, to be working with upgraded Nginx?

Well, I've just noticed that Nginx installation on Ubuntu comes with some sample in snippets/ folder:

tree /etc/nginx/snippets/                                          
├── fastcgi-php.conf
└── snakeoil.conf

0 directories, 2 files

The fastcgi-php.conf file is the one we use for setup of Nginx + PHP-FPM. These files are updated with Nginx and every time we have new Nginx, we should look into it to know how new configuration should be.