RewriteCond to match query string parameters in any order
I take a slightly different approach for this sort of thing, leveraging ENV VARs set and read by mod_rewrite. I find it more readable / maintainable to refer to the backreferences by name like this, and these ENV VARs can be reused later in request processing too. Overall I think it's a more powerful and flexible approach than the accepted answer here. In any case, it works well for me. I've copied my gist below in its entirety:
From https://gist.github.com/cweekly/5ee064ddd551e1997d4c
# Mod_rewrite is great at manipulating HTTP requests.
# Using it to set and read temp env vars is a helpful technique.
#
# This example walks through fixing a query string:
# Extract good query params, discard unwanted ones, reorder good ones, append one new one.
#
# Before: /before?badparam=here&baz=w00t&foo=1&bar=good&mood=bad
# After: /after?foo=1&bar=good&baz=w00t&mood=happy
#
# Storing parts of the request (or anything you want to insert into it) in ENV VARs is convenient.
# Note the special RewriteRule target of "-" which means "no redirect; simply apply side effects"
# This lets you manipulate the request at will over multiple steps.
#
# In a RewriteRule, set custom temp ENV VARs via [E=NAME:value]
# Note it's also possible to set multiple env vars
# like [E=VAR_ONE:hi,E=VAR_TWO:bye]
#
# You can read these values using %{ENV:VAR_NAME}e <- little "e" is not a typo
#
# Tangent:
# Note you can also read these env vars the same way, if you set them via SetEnvIf[NoCase]
# (It won't work to use SetEnv, which runs too early for mod_rewrite to pair with it.)
#
# Regex details:
# (?:) syntax means "match but don't store group in %1 backreference"
# so (?:^|&) is simply the ^ beginning or an & delimiter
# (the only 2 possibilities for the start of a qs param)
# ([^&]+) means 1 or more chars that are not an & delimiter
RewriteCond %{QUERY_STRING} (?:^|&)foo=([^&]+)
RewriteRule ^/before - [E=FOO_VAL:%1]
RewriteCond %{QUERY_STRING} (?:^|&)bar=([^&]+)
RewriteRule ^/before - [E=BAR_VAL:%1]
RewriteCond %{QUERY_STRING} (?:^|&)baz=([^&]+)
RewriteRule ^/before - [E=BAZ_VAL:%1]
RewriteRule ^/before /after?foo=%{FOO_VAL}e&bar=%{BAR_VAL}e&baz=%{BAZ_VAL}e&mood=happy [R=301,L]
P.S. This is not a copy/pasteable solution to your question, but rather shows exactly how to handle this kind of problem. Armed w this understanding, leveraging it for your example will be completely trivial. :)
You can achieve this with multiple steps, by detecting one parameter and then forwarding to the next step and then redirecting to the final destination
RewriteEngine On
RewriteCond %{QUERY_STRING} ^category=([^&]+) [NC,OR]
RewriteCond %{QUERY_STRING} &category=([^&]+) [NC]
RewriteRule ^index\.php$ $0/%1
RewriteCond %{QUERY_STRING} ^subcategory=([^&]+) [NC,OR]
RewriteCond %{QUERY_STRING} &subcategory=([^&]+) [NC]
RewriteRule ^index\.php/[^/]+$ $0/%1
RewriteCond %{QUERY_STRING} ^product=([^&]+) [NC,OR]
RewriteCond %{QUERY_STRING} &product=([^&]+) [NC]
RewriteRule ^index\.php/([^/]+/[^/]+)$ http://store.example.com/$1/%1/? [R,L]
To avoid the OR and double condition, you can use
RewriteCond %{QUERY_STRING} (?:^|&)category=([^&]+) [NC]
as @TrueBlue suggested.
Another approach is to prefix the TestString QUERY_STRING with an ampersand &, and check always
RewriteCond &%{QUERY_STRING} &category=([^&]+) [NC]
This technique (prefixing the TestString) can also be used to carry forward already found parameters to the next RewriteCond. This lets us simplify the three rules to just one
RewriteCond &%{QUERY_STRING} &category=([^&]+) [NC]
RewriteCond %1!&%{QUERY_STRING} (.+)!.*&subcategory=([^&]+) [NC]
RewriteCond %1/%2!&%{QUERY_STRING} (.+)!.*&product=([^&]+) [NC]
RewriteRule ^index\.php$ http://store.example.com/%1/%2/? [R,L]
The ! is only used to separate the already found and reordered parameters from the QUERY_STRING.