Convert various relative URLs to absolute

url_to_absolute.php

/**
 * Convert various relative urls to absolute
 *
 * @author Jan-Petter Gundersen (europe.jpg@gmail.com)
 * @param $url - url to convert
 * @param $base - parent url
 * @return string - absolute url
 */
function url_absolute($url, $base)
{
	// already absolute
	if (strpos($url, '://')) {
		return $url;
	}
	// shorthand scheme
	if (substr($url, 0, 2) == '//') {
		return parse_url($base, PHP_URL_SCHEME) . ':' . $url;
	}
	// queries and anchors
	if (substr($url, 0, 1) == '#' || substr($url, 0, 1) == '?') {
		return $base . $url;
	}
	// just add domain
	if (substr($url, 0, 1) == '/') {
		return parse_url($base, PHP_URL_SCHEME) . '://' . parse_url($base, PHP_URL_HOST) . $url;
	}
	// add slash to domain if needed
	if (stripos($base, '/', 9) === false) {
		$base .= '/';
	}
	// relative path
	$base_rel = parse_url($base, PHP_URL_PATH);
	$base_rel = substr($base_rel, 0, strrpos($base_rel, '/') + 1);
	while (strpos($url, '../') !== false) {
		$url = substr_replace($url, '', strpos($url, '../'), strlen('../'));
		$base_rel = substr($base_rel, 0, strrpos($base_rel, '/'));
		$base_rel = substr($base_rel, 0, strrpos($base_rel, '/') + 1);
	}
	if (substr($base_rel, 0, 1) != '/') {
		$base_rel = '/' . $base_rel;
	}
	return parse_url($base, PHP_URL_SCHEME) . '://' . parse_url($base, PHP_URL_HOST) . $base_rel . $url;
}