[Solved] Nginx / Error 502 / Upstream sent too big header

if the error log say :
… upstream sent too big header while reading response header from upstream …

then add in the nginx conf file of the app :

   fastcgi_buffers 16 16k;
   fastcgi_buffer_size 32k;

then verify the nginx conf
conf -t

if everything is ok, then reload nginx
service nginx reload

[source : http://www.dj-j.net/waka/Linux:Nginx_Erreur_502_Fastcgi_PHP ]

Thanks !