phpinfo() - is there an easy way for seeing it?

From your command line you can run..

php -i

I know it's not the browser window, but you can't see the phpinfo(); contents without making the function call. Obviously, the best approach would be to have a phpinfo script in the root of your web server directory, that way you have access to it at all times via http://localhost/info.php or something similar (NOTE: don't do this in a production environment or somewhere that is publicly accessible)

EDIT: As mentioned by binaryLV, its quite common to have two versions of a php.ini per installation. One for the command line interface (CLI) and the other for the web server interface. If you want to see phpinfo output for your web server make sure you specify the ini file path, for example...

php -c /etc/php/apache2/php.ini -i 

If you have php installed on your local machine try:

$ php -a
Interactive shell

php > phpinfo();

From the CLI the best way is to use grep like:

php -i | grep libxml