This site was not functional for most of the day. Depending on what time you came here, you may have seen anything from blank pages to dozens of PHP error messages. I was worried, because of the security problems in PHP, but it turned out, it was not an attack but an upgrade to the latest safe PHP version that broke things. Apparently it wasn’t a bug in PHP itself though, but an internal change (in relation with foreach) that broke some (or all?) of the popular byte-code optimizers/caches, namely Zend-Optimizer and TurckMMCache. I found this info over at the respective support-forums/bugtrackers:
While there is already a new release for the Zend-Optimzer, there is no new release (yet) of TurckMMCache. Since the lead developer announced that he would stop working on the project, because of starting to work for Zend, there have been no new releases. There was and still is talk of continuing the work on it (as you can also see in the above linked thread), but there seems to be nothing definite and official. APC may be a working (free) alternative, but the latest release is also several months back, so I don’t know wether it will have the same issue with 4.3.10. Otherwise it is probably better to go without the Optimizer for a while…