How do I apply URL normalization rules in PHP?

Question

Is there a pre-existing function or class for URL normalization in PHP?

Specifically, following the semantic preserving normalization rules laid out in this wikipedia article on URL normalization, (or whatever 'standard' I should be following).

Converting the scheme and host to lower case
Capitalizing letters in escape sequences
Adding trailing / (to directories, not files)
Removing the default port
Removing dot-segments

Right now, I'm thinking that I'll just use parse_url(), and apply the rules individually, but I'd prefer to avoid reinventing the wheel.

@ajreal no, not <link rel="canonical"...>. Just, normalizing a URL for, for example, requesting data about it from an API, particularly those that require that the URL be hashed, and so if you don't use a normalized URL, you'll get inaccurate or no results. — Yahel
– Yahel, Commented Nov 14, 2010 at 2:36
@yc : what is the diff between http://stackoverflow.com and http://stackoverflow.com// ? can u provide more example of url u try to avoid ? — ajreal
– ajreal, Commented Nov 14, 2010 at 4:33
Huge difference! The former hashes (md5) as 57f4dad48e7a4f7cd171c654226feb5a, the latter hashes as 8b34e6ecb6898f39350c1264d6d7aa6c. As far as I'm concerned, they're different URLs, even though a server will resolve the difference. There's a standard, as linked to, that seeks to create normalized URLs. I'm not inventing a concept here; there's a whole wiki article dedicated to the phenomenon. — Yahel
– Yahel, Commented Nov 14, 2010 at 15:10

Bharat Mediratta · Accepted Answer · 2010-11-14 03:28:07Z

6

The Pear Net_URL2 library looks like it'll do at least part of what you want. It'll remove dot segments, fix capitalization and get rid of the default port:

include("Net/URL2.php");
$url = new Net_URL2('HTTP://example.com:80/a/../b/c');
print $url->getNormalizedURL();

emits:

http://example.com/b/c

I doubt there's a general purpose mechanism for adding trailing slashes to directories because you need a way to map urls to directories which is challenging to do in a generic way. But it's close.

References:

answered Nov 14, 2010 at 3:28

Bharat Mediratta

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