As of this writing there exists a conflict with eAccelerator's default functionality and some core code in Drupal. Specifically, as part of its optimization process, eAccelerator removes comments & Annotations from PHP code. This presents a problem in Drupal because Doctrine, a library Drupal 8 uses relies on Annotations to work. This will cause a fatal error something to the effect of:
[Semantical Error] The class "Drupal\Core\Annotation\Plugin" is not annotated with @Annotation.
There are 2 options to address this problem:
- Disable eAccelerator and use either XCache or APC
- Recompile eAccelerator with flag --with-eaccelerator-doc-comment-inclusion