devot:eeDevoted to ExpressionEngine

Below is a list of variables it creates. There is also a prefix option in the extension settings, so you can create a prefix for all the variables, e.g. {url:referrer} instead of {referrer}. This started as a basic extension, and over the course of 2 years and 30+ EE sites it has grown a bit each time depending on what I needed. This also includes an old version of Low’s Seg2Cats extension, which works just as well as the new one, plus I added a couple of additional variables.

You may ask why the encoded URL options are available, but next time you need to pass a full URL as a query parameter in EE you’ll thank me (EE doesn’t like that).

Installation

Download the .zip from GitHub, extract the contents and rename the folder to url_helper and place it in your system/expressionengine/third_party folder, then go to Add-ons > Extensions in your control panel to enable it.

Variables

{last_segment} - returns the very last segment in the URI, even if it's a pagination segment
{last_segment_absolute} - returns the very last segment in the URI, but 2nd to last if the last is a pagination segment
{last_segment_id} - returns the ID of the last segment, in the case of /seg1/seg2/seg3/ it will return "3"
{last_segment_absolute_id} - return the ID of the last segment, or 2nd to last if the last is a pagination segment. In the case of /seg1/seg2/seg3/P5 it will return "3"
{parent_segment} - Will return the 2nd to last segment in the URI. In the case of /seg1/seg2/seg3/, it will return "seg2"
{all_segments} - /seg1/seg2/seg3/
{current_url} - http://www.mysite.com + segments + query string
{current_uri} - segments + query string
{current_url_encoded} - {current_url} base64encoded
{current_uri_encoded} - {current_uri} base64encoded
{query_string} - current query string including ?, returns blank if no query string exists
{referrer} - full referring/previous url visited
{referrer:segment_N} - fetch any segment from the referring url
{rev_segment_N} - segments reversed
{segment_N_category_id} 
{segment_N_category_name}
{segment_N_category_description}
{segment_N_category_image}
{last_segment_category_id}
{last_segment_category_name}
{last_segment_category_description}
{last_segment_category_image}
{segment_category_ids} - 2&6&9 - useful for doing an all inclusive search of the segments
{segment_category_ids_any} - 2|6|9 - useful for doing an all inclusive search of the segments

Provided by PHP's parse_url() method

{query} - current query string without ?
{scheme} - http, https, ftp etc
{host} - your domain name, e.g. localhost, site.com
{port} - any port number present in the URL, e.g. :80 or :8888
{path} - full folder/virtural folder path or all segments if your site is located at the root of the domain/vhost
{fragment} - anything after # in the URI
{user}
{pass}