A couple notes for those who are, like me, trying to run Symfony on PHP5 in Gentoo:

• You’ll need to make sure that magic_quotes_gpc is disabled.  It should be anyway, but I believe it defaults to “on.”
• You need to add “reflection” to the Gentoo useflags for dev-lang/php.  This functionality seems to be used by the symfony CLI app to build the propel models/sql/do inserts.

I’ll add more notes as I come across them.