Encode a URL (or just a path) with `rawurlencode()` to make it pass the W3C validator in HTML source and, of course, be a valid URL.

func.encode_url.inc.php

function encode_url($url) {
	$parsed_url = parse_url($url);
	$scheme   = isset($parsed_url['scheme']) ? $parsed_url['scheme'] . '://' : '';
	$host     = isset($parsed_url['host']) ? $parsed_url['host'] : '';
	$port     = isset($parsed_url['port']) ? ':' . $parsed_url['port'] : '';
	$user     = isset($parsed_url['user']) ? $parsed_url['user'] : '';
	$pass     = isset($parsed_url['pass']) ? ':' . $parsed_url['pass']  : '';
	$pass     = ($user || $pass) ? "$pass@" : '';
	$path     = isset($parsed_url['path']) ? $parsed_url['path'] : '';
	$query    = isset($parsed_url['query']) ? '?' . $parsed_url['query'] : '';
	$fragment = isset($parsed_url['fragment']) ? '#' . $parsed_url['fragment'] : '';
	return "$scheme$user$pass$host$port" . implode('/', array_map('rawurlencode', explode('/', $path))) . "$query$fragment";
}