gem install mysql error with Xampp


I'm trying to install mysql (to use it with Rails 2.2), without any
After browsing the web, I found some tips (I need to target the xampp
files), but it's still not working finally.

My command line is the following :
sudo gem install mysql --

Results :
Building native extensions. This could take a while...
ERROR: Error installing mysql:
  ERROR: Failed to build gem native extension.

extconf.rb install mysql --
checking for mysql_ssl_set()... yes
checking for mysql.h... no
checking for mysql/mysql.h... no
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.

Provided configuration options:

Gem files will remain installed in /Library/Ruby/Gems/1.8/gems/mysql-2.7
for inspection.
Results logged to /Library/Ruby/Gems/1.8/gems/mysql-2.7/gem_make.out

Do I have to install something else ? I found a developer package in
Xampp website, but I don't know if I have to use it and how to use it...

Anyone could help me?

Thank you very much.