Internals

In PHP, internals refers to everything under the hood of the language itself, not the code written with PHP.

Internals are the features written in C, C++ language and compiled with the engine; the Zend engine itself. It also refers to the contributors working on the core of PHP, as they are member of the internal mailing list.

See also PHP Internal Books.

Related : Zend Engine, Feature, Copy On Write (COW), Core, User Operations For Zend (UOPZ)