/**
* Returns the target URI as a relative reference from the base URI.
*
* This method is the counterpart to resolve():
*
* (string) $target === (string) UriResolver::resolve($base, UriResolver::relativize($base, $target))
*
* One use-case is to use the current request URI as base URI and then generate relative links in your documents
* to reduce the document size or offer self-contained downloadable document archives.
*
* $base = new Uri('http://example.com/a/b/');
* echo UriResolver::relativize($base, new Uri('http://example.com/a/b/c')); // prints 'c'.
* echo UriResolver::relativize($base, new Uri('http://example.com/a/x/y')); // prints '../x/y'.
* echo UriResolver::relativize($base, new Uri('http://example.com/a/b/?q')); // prints '?q'.
* echo UriResolver::relativize($base, new Uri('http://example.org/a/b/')); // prints '//example.org/a/b/'.
*
* This method also accepts a target that is already relative and will try to relativize it further. Only a
* relative-path reference will be returned as-is.
*
* echo UriResolver::relativize($base, new Uri('/a/b/c')); // prints 'c' as well
*
* @param UriInterface $base Base URI
* @param UriInterface $target Target URI
*
* @return UriInterface The relative URI reference
*/
public static function relativize(UriInterface $base, UriInterface $target)
{
if ($target->getScheme() !== '' && ($base->getScheme() !== $target->getScheme() || $target->getAuthority() === '' && $base->getAuthority() !== '')) {
return $target;
}
if (Uri::isRelativePathReference($target)) {
// As the target is already highly relative we return it as-is. It would be possible to resolve
// the target with `$target = self::resolve($base, $target);` and then try make it more relative
// by removing a duplicate query. But let's not do that automatically.
return $target;
}
if ($target->getAuthority() !== '' && $base->getAuthority() !== $target->getAuthority()) {
return $target->withScheme('');
}
// We must remove the path before removing the authority because if the path starts with two slashes, the URI
// would turn invalid. And we also cannot set a relative path before removing the authority, as that is also
// invalid.
$emptyPathUri = $target->withScheme('')->withPath('')->withUserInfo('')->withPort(null)->withHost('');
if ($base->getPath() !== $target->getPath()) {
return $emptyPathUri->withPath(self::getRelativePath($base, $target));
}
if ($base->getQuery() === $target->getQuery()) {
// Only the target fragment is left. And it must be returned even if base and target fragment are the same.
return $emptyPathUri->withQuery('');
}
// If the base URI has a query but the target has none, we cannot return an empty path reference as it would
// inherit the base query component when resolving.
if ($target->getQuery() === '') {
$segments = explode('/', $target->getPath());
$lastSegment = end($segments);
return $emptyPathUri->withPath($lastSegment === '' ? './' : $lastSegment);
}
return $emptyPathUri;
}
