Заголовок уходит верный - вот что получается на локальном без опенкарта
{"Host":"test-bit.local","Authorization":"Basic YWRtaW46MTExMTE=","User-Agent":"1C+Enterprise\/8.3","Content-Encoding":"gzip","Accept-Encoding":"gzip","Connection":"keep-alive","Content-Type":"application\/json","Accept":"*\/*","Content-Length":"20"}{"Host":"test-bit.local","Authorization":"Basic YWRtaW46MTExMTE=","User-Agent":"1C+Enterprise\/8.3","Content-Encoding":"gzip","Accept-Encoding":"gzip","Connection":"keep-alive","Content-Type":"application\/json","Accept":"*\/*","Content-Length":"20"}
а если отправлять на сайт тогда
2020-07-07 16:45:45 - Array
(
[Content-Length] => 0
[Content-Type] => application/octet-stream
[Cookie] => OCSESSID=3a6cac31bafa237f4cba6abdd5; language=ru-ru; currency=RUB
[Accept] => */*
[Connection] => keep-alive
[Accept-Encoding] => gzip
[Content-Encoding] => gzip
[User-Agent] => 1C+Enterprise/8.3
[Authorization] => Basic dGVzdDpLMGEyQjV0NA==