Quick tip: If you’re getting 502 Bad Gateway errors after upgrading your Debian Wheezy Nginx server to PHP5-FPM 5.5.5 then check out your www.conf file. Look for these lines:
;listen.owner = www-data
;listen.group = www-data
Uncomment them by removing the ‘;’ in front of all these lines so it looks like:
listen.owner = www-data
listen.group = www-data
Then load the new settings into PHP, which on my Nginx servers usually is done with:
service php5-fpm reload