Why doesn't the web server return the entire response?

Question

PHP

For some reason, the server does not return a complete response.
Those. the script is being executed. At the end "echo $response;". The output should be full-fledged JSON, but I get truncated text.
If you do "file_put_contents('response.log', $response)" right before echo, then the file will contain the required full-fledged JSON.
nginx web server.

Answer 1

The problem was that the /var/lib/nginx directory was not writable. Changed the owner to nginx and everything worked out.

Answer 2

Try checking the response headers.
Namely Content-Length