Problem

I have a request from my client to update an old (~3 years) CodeIgniter application. Copied the code into nginx's root directory, configure it, and then this is the very first issue I found:

<omitted for brevity> upstream sent too big header while reading response header from upstream, client: <omitted for brevity>

Solution

On nginx's configuration file, add this php location block (location ~ .php$):

fastcgi_buffer_size 128k;
fastcgi_buffers 4 256k;
fastcgi_busy_buffers_size 256k;