PHP Curl Error: 417-expectation Failed

When I add a piece of content to the post submission, I get an error: 417-expectation Failed.

Data found that when using curl for post, when the post data is greater than 1024 bytes, curl does not directly initiate the POST request, but is divided into two steps,

1. Send a request that contains a exc:100-continue that asks the server to receive the data

2. After receiving the server return 100-continue answer, the post is submitted to the server

RFC related information: https://www.w3.org/Protocols/rfc2616/rfc2616-sec8.html#sec8.2.3

However, my router is using LIGHTHTTPD, it does not answer 100-continue correctly, so it returns 417 this error

The workaround is to add this option:curl_setopt ($ch, Curlopt_httpheader, Array (' Expect: '));

PHP Curl Error: 417-expectation Failed