Remember - *nix filenames may contain weird characters including line-breaks. If you adjust the example call as below then this will be handled. I realize that you are running this on your own files and probably know that they will never contain weird characters, but it's probably better to handle the weird cases as a matter of course so that they are handled if they ever do crop up.

find /usr/share/php -name "*.php" -o -name "*.inc" -print0 | xargs -0 count-code

This causes find to use the NUL character to separate the results - and causes xargs to expect that too.