These days after all the cleanups, the "php" package (vs php-common) pretty much just contains Apache HTTPD-related stuff:
# rpm -ql php /etc/httpd/conf.d/php.conf /usr/lib/httpd/modules/libphp5.so /var/lib/php/session /var/www/icons/php.gif
So in theory it should be OK to remove this if you need PHP but not the HTTPD stuff (for example if you are using CGI or CLI only).
However, you'll notice /var/lib/php/session in the above list. This doesn't seem to be specific to HTTPD and indeed is useful if you are using php-cgi from a webserver. Indeed, the path is compiled into the binaries; for example:
$ php-a Interactive shell
php > echo ini_get('session.save_path'); /var/lib/php/session
So I think we should probably move it to php-common - what do others think?
Tim