What does the error FastCGI sent in stderr:?

Once I confess - I'm a novice. In the logs found a recurring error FastCGI sent in stderr:

what does it mean?
July 12th 19 at 17:25
1 answer
July 12th 19 at 17:27
"FastCGI sent in stderr" is not a mistake. Error hereinafter. And it's just a sign that the script is running подfastcgi, spit out error

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