PHP5 should be a different ebuild, not another version of PHP. PHP5 is not in every case backwards compatible with php4 and scripts must often be rewritten or changed. There is also a need for installing both versions side by side, because some scripts depend on version 4, some on 5. Therefore the v5 executable can't be /usr/bin/php - /usr/bin/php5 seems to me as a good choice. Reproducible: Always Steps to Reproduce: 1. emerge php Expected Results: n.a. n.a.
We don't do such things in Gentoo, we have SLOTs for that.