Usually this method does not need to be called manually but instead is used indirectly via
Psr\Http\Message\UriInterface::__toString.
PSR-7 UriInterface treats an empty component the same as a missing component as
getQuery(), getFragment() etc. always return a string. This explains the slight
difference to RFC 3986 Section 5.3.
Another adjustment is that the authority separator is added even when the authority is missing/empty
for the "file" scheme. This is because PHP stream functions like file_get_contents only work with
file:///myfile but not with file:/myfile although they are equivalent according to RFC 3986. But
file:/// is the more common syntax for the file scheme anyway (Chrome for example redirects to
that format).
/**
* Converts the relative URI into a new URI that is resolved against the base URI.
*
* @param UriInterface $base Base URI
* @param UriInterface $rel Relative URI
*
* @return UriInterface
* @link http://tools.ietf.org/html/rfc3986#section-5.2
*/
public static function resolve(UriInterface $base, UriInterface $rel)
{
if ((string) $rel === '') {
// we can simply return the same base URI instance for this same-document reference
return $base;
}
if ($rel->getScheme() != '') {
return $rel->withPath(self::removeDotSegments($rel->getPath()));
}
if ($rel->getAuthority() != '') {
$targetAuthority = $rel->getAuthority();
$targetPath = self::removeDotSegments($rel->getPath());
$targetQuery = $rel->getQuery();
} else {
$targetAuthority = $base->getAuthority();
if ($rel->getPath() === '') {
$targetPath = $base->getPath();
$targetQuery = $rel->getQuery() != '' ? $rel->getQuery() : $base->getQuery();
} else {
if ($rel->getPath()[0] === '/') {
$targetPath = $rel->getPath();
} else {
if ($targetAuthority != '' && $base->getPath() === '') {
$targetPath = '/' . $rel->getPath();
} else {
$lastSlashPos = strrpos($base->getPath(), '/');
if ($lastSlashPos === false) {
$targetPath = $rel->getPath();
} else {
$targetPath = substr($base->getPath(), 0, $lastSlashPos + 1) . $rel->getPath();
}
}
}
$targetPath = self::removeDotSegments($targetPath);
$targetQuery = $rel->getQuery();
}
}
return new Uri(Uri::composeComponents($base->getScheme(), $targetAuthority, $targetPath, $targetQuery, $rel->getFragment()));
}