After upgrading php-fpm, my PHP-based sites were returning “502 Bad Gateway” errors. Here’s how I managed to solve it.
Check to make sure that php-fpm is running with
ps auxww | grep php – if you can’t see any php-fpm processes in the output, then you may need to re-install php-fpm. If php-fpm is running okay, then skip this first step.
sudo apt-get remove php5 php5-cgi php5-fpm sudo apt-get install php5 php5-cgi php5-fpm
The thing to notice here is that the order in which you install the packages is important. In the past I have found that installing them in the wrong order causes the packages to be configured incorrectly.
Next, get php-fpm to listen on the correct host/port. In
/etc/php5/fpm/pool.d/www.conf change the following line from:
listen = /var/run/php5-fpm.sock
listen = 127.0.0.1:9000
Restart php-fpm with
sudo /etc/init.d/php-fpm restart and everything should work normally again.