I used this invocation to avoid some problems that we had in the past with some of the newer PHP code:
ctags -R --languages=php --exclude="CVS" --php-kinds=f --regex-PHP='/abstract class ([^ ]*)/\1/c/' --regex-PHP='/interface ([^ ]*)/\1/c/' --regex-PHP='/(public |static |abstract |protected |private )+function ([^ (]*)/\2/f/'
This (and any of the other ctags strings above) don't work on the BSD ctags which comes with Mac OS X so we need a different solution there.