use setBody instead to have the not deprecated version.
(PECL pecl_http 0.14.0-1.4.1)
HttpRequest::setRawPostData — Set raw post data
Set raw post data to send, overwriting previously set raw post data. Don't forget to specify a content type. Affects only POST and custom requests.
Only either post fields or raw post data can be used for each request. Raw post data has higher precedence and will be used even if post fields are set.
This function alias is DEPRECATED and only exists for backwards compatibility reasons. The use of this function is not recommended, as it may be removed from PHP in the future. HttpRequest::setBody() should be used instead.
raw post data
TRUE on success or
FALSE on failure.