php - Nginx 502 FastCGI Error -

when try access page on server, returns 502 gateway error. (sometimes works reload page , shows 502 gateway page again).

if check nginx error logs, error comes up:

2017/09/13 19:14:49 [error] 3762#3762: *22 upstream prematurely closed fastcgi stdout while reading response header upstream, client: serverip, server: localhost, request: "get /inventory.php http/1.1", upstream: "fastcgi://unix:/run/php/php7.0-fpm.sock:", host: "localhost", referrer: "localhost" 

i tried looking error on google, no solutions far, , wondering if knows error & how fix it.

thanks.

edit 1:

• fastcgi_buffers set this:

fastcgi_buffers 16 16k;

fastcgi_buffer_size 120k;

try increase values of next settings:

fastcgi_buffer_size fastcgi_buffers 

https://nginx.ru/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_buffer_size https://nginx.ru/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_buffers