php-5.1.0_beta uses the eclass php5-sapi-r3, but mod_php-5.1.0_beta still uses php5-sapi-r2. Is that correct?
Thanks for spotting that. mod_php-5.1.0_beta has now been updated to use php5- sapi-r3. This change should appear on your local rsync mirror in about an hour. Best regards, Stu