In this quick new post to his blog Mark Story talks about two new errors he ran across when upgrading his installation to PHP 5.4, both showing up under E_ALL.
I've been running the PHP5.4 RC builds for the last few months, and there are some interesting changes in the upcoming PHP release. On top of all the great new features coming in PHP5.4. After updating to PHP5.4-RC4, a few things that used to not trigger errors and silently do the wrong thing, now trigger notices or warnings.
The two he mentions deal with a new warning on illegal string offsets and the other about string offsets ("Notice: String offset cast occurred"). You can find out about more changes in the PHP 5.4 series in the various Changelogs for each Release Candidate and beta release.