Htaccess : multiple parameters and nested parentheses

Question

I've got some project where I redirect every request on index.php, with various GET parameters.

Currently, I'm using this kind of htaccess (this is only an extract, and I changed parameters name to a, b, c..., in order to simplify the problem) :

RewriteRule ^([\w-]+)\.html$                   index.php?a=$1 [L]
RewriteRule ^([\w-]+)/([\w-]+)\.html$          index.php?a=$1&b=$2 [L]
RewriteRule ^([\w-]+)/([\w-]+)/([\w-]+)\.html$ index.php?a=$1&b=$2&c=$3 [L]
(...)

It works (well), but I was thinking about a way to minify those lines into a single one. The idea is to have some nested parentheses to 'generate' all GET parameters, but it seems it won't work as easily as I thought.

Here is what I've made so far :

RewriteRule 
    ^(?:([\w-]+)\/)*([\w-]+)\.html$ 
    index.php?a=$1&b=$2&c=$3&d=$4&e=$5&f=$6&g=$7&h=$8&i=$9 [L]

GET result for the url http://website.com/1/2/3/4/5/6/7/8/9.html :

array(9) { 
   ["a"]=> string(1) "8" 
   ["b"]=> string(1) "9" 
   ["c"]=> string(0) "" 
   ["d"]=> string(0) "" 
   ["e"]=> string(0) "" 
   ["f"]=> string(0) "" 
   ["g"]=> string(0) "" 
   ["h"]=> string(0) "" 
   ["i"]=> string(0) "" 
}

Instead of get a=1, b=2, c=3... I only receive the two last parameters. Notice that the RewriteRule is executed, then I know my regex match.

Any idea ?

Answer 1

For the record: do consider using a PHP-based approach: pass the entire requested URI to PHP, and then you could handle the whole thing in PHP, which is a whole lot easier, very likely safer, and maybe even faster, than doing the magic with mod_rewrite.

I mean something like this:

 RewriteRule ^(.*)\.html$ switchboard.php?uri=$1 [L]

then in switchboard.php:

list($_GET['a'], $_GET['b'], $_GET['c']) = explode( '/', $_GET['uri']);
require 'index.php';

(if the super-long list() looks cumbersome, you may use some clever one-liner mapping technique)

Anyhow, the regex question is certainly interesting, but it's a generic PCRE thing. The phenomenon is called "repeated capture group": whenever you repeat a capture group with the Kleene star like you do, only the very last iteration will actually be captured (in our case, the matches 1,2..7 were discarded, and only the 8 was kept) - imagine it as a buffer you keep overwriting with newer and newer matches. It makes a lot of sense, if you think about it.

A solution is to use as many groups as you actually want to capture, by making the earlier groups optional - it's incredibly awkward to write and read (indeed, Arjan just posted it, and it's a headache just to look at it), and also very inefficient in this case. A much simpler solution is to just capture the whole thing and split it.

Answer 2

RewriteRule 
    ^([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+)(?:\/([\w-]+))?)?)?)?)?)?)?)?\.html$ 
    index.php?a=$1&b=$2&c=$3&d=$4&e=$5&f=$6&g=$7&h=$8&i=$9 [L]

Untested, but I think this does what you want. Note that it works for 1 to 9 parameters, it requires at least one. Also note that any GET parameter that was present in the original url could be removed this way.