PHP convert external relative path to absolute path - php

Question

I am trying to figure out how to convert an "external relative path" to an absolute one:
I'd really like a function that will do the following:
$path = "/search?q=query";
$host = "http://google.com";
$abspath = reltoabs($host, $path);
And have $abspath equal to "http://google.com/search?q=query"
Another example:
$path = "top.html";
$host = "www.example.com/documentation";
$abspath = reltoabs($host, $path);
And have $abspath equal to "http://www.example.com/documentation/top.html"
The problem is that it is not guaranteed to be in that format, and it could already be absolute, or be pointing to a different host entirely, and I'm not quite sure how to approach this.
Thanks.

Answer 1

You should try the PECL function http_build_url
http://php.net/manual/en/function.http-build-url.php

Answer 2

So there are three cases:
proper URL
no protocol
no protocol and no domain
Example code (untested):
if (preg_match('#^http(?:s)?://#i', $userurl))
$url = preg_replace('#^http(s)?://#i', 'http$1://', $userurl); //protocol lowercase
//deem to have domain if a dot is found before a /
elseif (preg_match('#^[^/]+\\.[^/]+#', $useurl)
$url = "http://".$useurl;
else { //no protocol or domain
$url = "http://default.domain/" . (($useurl[0] != "/") ? "/" : "") . $useurl;
}
$url = filter_var($url, FILTER_VALIDATE_URL);
if ($url === false)
die("User gave invalid url").

Answer 3

It appears I have solved my own problem:
function reltoabs($host, $path) {
$resulting = array();
$hostparts = parse_url($host);
$pathparts = parse_url($path);
if (array_key_exists("host", $pathparts)) return $path; // Absolute
// Relative
$opath = "";
if (array_key_exists("scheme", $hostparts)) $opath .= $hostparts["scheme"] . "://";
if (array_key_exists("user", $hostparts)) {
if (array_key_exists("pass", $hostparts)) $opath .= $hostparts["user"] . ":" . $hostparts["pass"] . "#";
else $opath .= $hostparts["user"] . "#";
} elseif (array_key_exists("pass", $hostparts)) $opath .= ":" . $hostparts["pass"] . "#";
if (array_key_exists("host", $hostparts)) $opath .= $hostparts["host"];
if (!array_key_exists("path", $pathparts) || $pathparts["path"][0] != "/") {
$dirname = explode("/", $hostparts["path"]);
$opath .= implode("/", array_slice($dirname, 0, count($dirname) - 1)) . "/" . basename($pathparts["path"]);
} else $opath .= $pathparts["path"];
if (array_key_exists("query", $pathparts)) $opath .= "?" . $pathparts["query"];
if (array_key_exists("fragment", $pathparts)) $opath .= "#" . $pathparts["fragment"];
return $opath;
}
Which seems to work pretty well, for my purposes.