Once installed, eAccelerator optimizes the compiled bytecode and caches this to shared memory or disk or both.
This avoids the performance overhead of repeated parsing and compilation.
Previous eAccelerator versions also provided functions[1] for use in PHP scripts that allow access to shared memory, automatic web (content) caching, and other related tasks.
Old eAccelerator versions had an encoder component that creates a file that cannot be as easily read as a normal PHP script, offering some code protection.
This functionality has been removed from the current developer version and will not be part of the next release.