wp_get_server_protocol()

wp_get_server_protocol(): string

function wp_get_server_protocol() {
	$protocol = $_SERVER['SERVER_PROTOCOL'] ?? '';

	if ( ! in_array( $protocol, array( 'HTTP/1.1', 'HTTP/2', 'HTTP/2.0', 'HTTP/3' ), true ) ) {
		$protocol = 'HTTP/1.0';
	}

	return $protocol;
}