I had a similar problem trying to feed huge ingestion files to elasticsearch's bulk API from PHP, until I realized that the bulk API endpoint accepted PUT requests. Anyway, this code performs POST requests with huge files:

$curl = curl_init();
curl_setopt( $curl, CURLOPT_PUT, 1 );
curl_setopt( $curl, CURLOPT_INFILESIZE, filesize($tmpFile) );
curl_setopt( $curl, CURLOPT_INFILE, ($in=fopen($tmpFile, 'r')) );
curl_setopt( $curl, CURLOPT_CUSTOMREQUEST, 'POST' );
curl_setopt( $curl, CURLOPT_HTTPHEADER, [ 'Content-Type: application/json' ] );
curl_setopt( $curl, CURLOPT_URL, $url );
curl_setopt( $curl, CURLOPT_RETURNTRANSFER, 1 );
$result = curl_exec($curl);
curl_close($curl);
fclose($in);

Here, $tmpFile is the full path of the file containing the request body.

NOTE: The important part is setting CURLOPT_CUSTOMREQUEST to 'POST' even though CURLOPT_PUT is set.

You'd have to adapt the Content-Type: header to whatever the server is expecting.

Using tcpdump, I could confirm the request method to be POST:

POST /my_index/_bulk HTTP/1.1
Host: 127.0.0.1:9200
Accept: */*
Content-Type: application/json
Content-Length: 167401
Expect: 100-continue

[...snip...]

I'm using packages libcurl3 (version 7.35.0-1ubuntu2.5) and php5-curl (version 5.5.9+dfsg-1ubuntu4.11) on Ubuntu 14.04.