• What this plugin does
• Why bother?
• Design principals
  • Backward compatible
  • Speed is king
  • Human readable
  • Automatic
• How it works
  • Rewrite outgoing links
  • Rewrite incoming links
  • Base href
  • Canonical link
  • History replaceState
• Installation

It makes url's clean! Some real example url's:

• A course page:

/course/MATH101

• A module page:

/course/MATH101/lesson/6-how-to-do-matrix-multiplication

• A user profile:

/user/brendan

Good URL design is a hall mark of properly engineered internet systems. That said URL's have long been poorly implemented in many systems, moodle included, to the point where browsers are now hiding URL's because they are so ugly and opaque.

For the canonical guide to good URL's refer to Tim Berners-Lee timeless page:

http://www.w3.org/Provider/Style/URI

There are many benefits to end users, but admittedly some of these are fading:

• Human readable URL's when shared or embedded in social media
• Better context of a page, eg what course is this forum in
• 'Hackable' urls, going 'up' and also guessing urls is easier

But despite the fading of importance of URL's to browsers and users there are still many reasons why clean urls are a good thing:

• Much better filtering and reporting in log files and analytics software
• More resilient links when migrating systems (eg backup and restore to a new moodle but mostly keep your urls the same)
• Deterministic linking in from external pages, (eg deep link from a course catalog or staff directly into moodle)

URL's must always work, old and new. Old url's should be seamlessly upgrade to new url's where possible.

Some url rewrites such as those involving a course shortcode or username instead of id's, maybe be brittle if your site allows these things to change, so these are optional.

Speed is an integral part of the user experience. So we want to avoid things like 302 redirects, cache internally any expensive processing. If a url is never going to be seen by an end user, then avoid cleaning it.

A typical moodle url looks like this:

/mod/forum/view.php?id=6

This is fairly opaque and tells us very little. We should add extra information into the url to make it readable, giving it context, whilst at the same time removing extaneous information such as the php extension. eg

/course/MATH101/lesson/6-how-to-do-matrix-multiplication

Note we have also added redundant heirarchical information, ie the course path components. This immediately gives context, but is also useful to non humans, such as for Google Analytics to create 'drill down' reports.

Moodle already has rich meta data which we can leverage to produce clean url's. We don't want the site admins, let alone the teachers, to have to do anything extra. It should Just Work.

This plugin adds a very small hack to the moodle_url->out() method which cleans the links that moodle renders onto a page. It applies a variety of safe tranformations, and if the more aggressive settings are on, it applies some much deeper tranformations by reaching into the moodle navigation heirarchy to add extra redundant path elements to the url. Unfortunately we can't often read this information until we are on the page that uses them, or a nearby page, so the first time we render that page we clean the url and cache it for next time.

Incoming links are diverted by an apache rewrite rule to router.php, which then uncleans the url and passes it back into moodle which doesn't know anything was different.

Not every moodle link uses moodle_url, and some may also use relative links. Because the clean url may be wildy different to the original, these legacy links will break. To fix this, we add a base href tag of the original url to any pages with a rewritten url. An example of these are the module index pages which use relative links to the discussions.

/mod/forum/index.php?id=4

If a robot like google is scraping your page, we don't want to split the pagerank between the old and clean url, and we want to ensure that google always sends people to the clean url. We acheive this by rendering a 'canonical' link in the HTML head. This is similar to a 302 redirect but just for robots, and doesn't incur a roundtrip penalty.

http://en.wikipedia.org/wiki/Canonical_link_element

This also now makes it much easier to manage parts of your site using robots.txt

The are many ways a url gets shared, copy and paste, a 'share' widget etc. We want the url to be correct as soon as possible, so even if the link we clicked on was an normal moodle url, we replace this as soon as possible using html5 history.replaceState()

We also need to do this early, before things that use the url such as a Google Analytics tracking code. We want the url's to be nice in GA so we get clean 'drill down' report etc

The only down side to this approach is if you have outbound link tracking on the referring page.

https://developer.mozilla.org/en-US/docs/Web/Guide/API/DOM/Manipulating_the_browser_history#The_replaceState()_method

eg using git submodule:

git submodule add [email protected]:brendanheywood/moodle-local_cleanurls.git local/cleanurls

Ideally all of this code would be in a plugin and only use core api's (but the api's we need don't exist yet), or it would be bundled into core. In the mean time touches to two places are needed:

1. moodle_url in lib/weblib.php to intercept outgoing urls
2. standard_head_html() in lib/outputrenderers.php to include head related fixes

You can apply it in one line:

git apply local/cleanurls/core.patch

This patch it also available in github:

https://github.com/brendanheywood/moodle/tree/MDL-28030-cleanurls

It was built using git like this

git format-patch xyz123 --stdout > local/cleanurls/core.patch

<Directory /var/www/your/moodle/path>
   RewriteEngine on
   RewriteBase /
   RewriteCond %{REQUEST_FILENAME} !-f
   RewriteCond %{REQUEST_FILENAME} !-d
   RewriteRule ^(.*)$ local/cleanurls/router.php?q=$1 [L,QSA]
</Directory>

Now restart apache

Go to the /admin/settings.php?section=local_cleanurls settings page and it should show a green success message if it detects the router rewrite is in place and working.

Now you can Tick the box turning on the rewrites and tune the other options If you have any issues then turn on the rewrite logging and tail your apache log for details.

• Pull requests welcome!
• You may find that certain links in moodle core, or particular plugins don't use moodle_url - so best patch them and push back upstream