According to your phpinfo() you have to recompile php.
Download the source code (get the latest version 4.3.10 which fixes some bugs) from
http://www.php.net and use something like:
Code:
./configure --with-apxs2=/path/to/apache/bin/apxs --with-xml --other-options-you-need
make
make install (as root)
Take a look at you apache config file to see if you have to change the path to libphp4.so and then restart apache.
Regards