WordPress at a glance
filter is not described

wp_http_ixr_client_headers filter-hook . WP 4.4.0

Filters the headers collection to be sent to the XML-RPC server.

Usage

add_filter( 'wp_http_ixr_client_headers', 'filter_function_name_1968' );
function filter_function_name_1968( $headers ){
	// filter...

	return $headers;
}
$headers(array)
Array of headers to be sent.

Where the hook is called

WP_HTTP_IXR_Client::query()
wp-includes/class-wp-http-ixr-client.php 78
$args['headers'] = apply_filters( 'wp_http_ixr_client_headers', $args['headers'] );

Where the hook is used (in WP core)

Does not used.