If you apt-get install phpmyadmin on Debian/Ubuntu, you will notice the quoted warning message:
Server running with Suhosin. Please refer to documentation for possible issues.
You will get reference and possibile solutions here.
A fast get to achieve a fully working phpmyadmin on a trusted environment, is to enable the simulation mode on the phpmyadmin vhost, editing /etc/apache2/conf.d/phpmyadmin.conf [...]