Check if the file exists.

[Felix Quintana]

I'm trying to check if the file exists before passing it to fastcgi but I have not found as.
This is what I'm doing:
            #if (!-f $document_root$fastcgi_script_name)

            if (!-f $request_filename)             
            {
                return 404;
            }

I've tried try_files but not find a way.
The file is of the form:
/web/app.php/asd/fgh?ert=xx

If it let me pass over fastcgi returns the error:
No input file specified. 
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