You shouldn't have to set the content-length yourself.
If you use cURL to send an HTTP POST,
it will calculate the content length for you.
If you set the CURLOPT_POSTFIELDS value as an array,
it will automatically submit the request as multipart/form-data and use a boundary.
If you pass a string, it will use application/x-www-form-urlencoded
so make sure you pass a urlencoded string to CURLOPT_POSTFIELDS and
not an array since you want form-urlencoded.

<?php
/** * Returns the size of a file without downloading it, or -1 if the file * size could not be determined. * * @param $url - The location of the remote file to download. Cannot * be null or empty. * * @return The size of the file referenced by $url, or -1 if the size * could not be determined. */
function curl_get_file_size( $url ) { // Assume failure. $result = -1; $curl = curl_init( $url ); // Issue a HEAD request and follow any redirects. curl_setopt( $curl, CURLOPT_NOBODY, true ); curl_setopt( $curl, CURLOPT_HEADER, true ); curl_setopt( $curl, CURLOPT_RETURNTRANSFER, true ); curl_setopt( $curl, CURLOPT_FOLLOWLOCATION, true ); curl_setopt( $curl, CURLOPT_USERAGENT, get_user_agent_string() ); $data = curl_exec( $curl ); curl_close( $curl ); if( $data ) { $content_length = "unknown"; $status = "unknown"; if( preg_match( "/^HTTP\/1\.[01] (\d\d\d)/", $data, $matches ) ) { $status = (int)$matches[1]; } if( preg_match( "/Content-Length: (\d+)/", $data, $matches ) ) { $content_length = (int)$matches[1]; } // http://en.wikipedia.org/wiki/List_of_HTTP_status_codes if( $status == 200 || ($status > 300 && $status <= 308) ) { $result = $content_length; } } return $result;
}
?>