WordPress at a glance
function is not described

wp_get_server_protocol() WP 4.4.0

Return the HTTP protocol sent by the server.

No Hooks.

Return

String. The HTTP protocol. Default: HTTP/1.0.

Usage

wp_get_server_protocol();

Code of wp get server protocol: wp-includes/load.php VER 5.0.3

<?php
function wp_get_server_protocol() {
	$protocol = $_SERVER['SERVER_PROTOCOL'];
	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0' ) ) ) {
		$protocol = 'HTTP/1.0';
	}
	return $protocol;
}