You should view http://nginx.org/en/docs/http/ngx_http_fastcgi_module.html#fastcgi_catch_stderr
Might be what you seek for a empty blank page output or specific text that would be a Fatal error etc.

CJ Ess Wrote:
-------------------------------------------------------
> My employer uses Nginx in front of PHP-FPM to generate their web
> content.
> They have PHP's error reporting shut off in production so when
> something
> does go wrong in their PHP scripts they end up with a "White Screen Of
> Death". From a protocol level the white screen of death is a 200
> response
> with no content. They were wondering if there was a way to detect the
> WSOD
> within Nginx and substitute their 500 error page.
>
> PHP-FPM typically uses chunked encoding so I don't think the
> content-length
> header is going to help me.
>
> Does anyone have any suggestions how I might best accomplish this?
>
> I looked around with Google but all of the hits were people wanting to
> turn
> on error reporting, or looking help getting php-fpm working with Nginx
> to
> begin with.
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