Grab more than 2 parameters using RewriteCond - apache

Question

I have a URL with 4 query parameters:
https://address.com/bin/servlet?firstKey=firstValue&secondKey=secondValue&thirdKey=thirdValue
I would to map this URL to path variables:
https://address.com/content/firstValue/secondValue/thirdValue
This is what I'm trying to do:
RewriteCond %{QUERY_STRING} &?firstKey=([^&]+)&?secondKey=([^&]+) [NC]
Then rewriting rule:
RewriteRule ^/bin/servlet /content/%1/%2 [QSD,PT]
This is working fine.
But the pain is: Third parameter, when I'm adding 3rd key like other 2 parameters it won't work.
RewriteCond %{QUERY_STRING} &?firstKey=([^&]+)&?secondKey=([^&]+)&?thirdKey=([^&]+) [NC]
RewriteRule ^/bin/servlet /content/%1/%2/%3 [QSD,PT]

Answer 1

There are a number of issues with your implementation, for example the usage of "&" in the condition. But in general there is no limit to the number of parameters you can detect and handle with your chose strategy.
I made a few adjustments, this probably is what you are looking for:
RewriteEngine on
RewriteCond %{QUERY_STRING} ^firstKey=([^&]+)&secondKey=([^&]+)&thirdKey=([^&]+)$
RewriteRule ^/?bin/servlet$ /content/%1/%2/%3 [R=301,QSD,L]
RewriteRule ^/?content/([^/]+)/([^/]+)/([^/]+)/?$ /bin/servlet?firstKey=$1&secondKey=$2&thirdKey=$3 [L,QSA]
This obviously only handles requests using exactly three parameters. It is possible to generalize such approach to be able to handle a dynamic number of parameters, but I would advise against it: often it is better to keep things less complex, so just add corresponding rules for 2 and 4 parameters, if required. That way you will be able to maintain and extend the solution easily.
UPDATE:
In your comment below you ask if it is possible to capture argument values specified in arbitrary order. Sure, everything is possible, but things get a bit more complex then. Take a look at this example:
RewriteEngine on
RewriteCond %{QUERY_STRING} (?:^|&)firstKey=([^&]+)(?:&|$)
RewriteRule ^/?bin/servlet$ - [E=FIRST_VAL:%1]
RewriteCond %{QUERY_STRING} (?:^|&)secondKey=([^&]+)(?:&|$)
RewriteRule ^/?bin/servlet$ - [E=SECOND_VAL:%1]
RewriteCond %{QUERY_STRING} (?:^|&)thirdKey=([^&]+)(?:&|$)
RewriteRule ^/?bin/servlet$ - [E=THIRD_VAL:%1]
RewriteRule ^/?bin/servlet$ /content/%{ENV:FIRST_VAL}/%{ENV:SECOND_VAL}/%{ENV:THIRD_VAL} [R=301,QSD,L]
RewriteRule ^/?content/([^/]+)/([^/]+)/([^/]+)/?$ /bin/servlet?firstKey=$1&secondKey=$2&thirdKey=$3 [L,QSA]