# Foreign Function Interface

&reftitle.intro;

This extension allows the loading of shared libraries (`.DLL` or `.so`), calling of C functions and accessing of C data structures in pure PHP, without having to have deep knowledge of the Zend extension API, and without having to learn a third “intermediate” language. The public API is implemented as a single class `FFI` with several static methods (some of them may be called dynamically), and overloaded object methods, which perform the actual interaction with C data.

FFI is dangerous, since it allows to interface with the system on a very low level. The FFI extension should only be used by developers having a working knowledge of C and the used C APIs. To minimize the risk, the FFI API usage may be restricted with the ffi.enable &php.ini; directive.

The FFI extension does not render the classic PHP extension API obsolete; it is merely provided for ad-hoc interfacing with C functions and data structures.

Currently, accessing FFI data structures is significantly (about 2 times) slower than accessing native PHP arrays and objects. Therefore, it makes no sense to use the FFI extension for speed; however, it may make sense to use it to reduce memory consumption.

&reference.ffi.setup; &reference.ffi.examples; &reference.ffi.ffi; &reference.ffi.ffi.cdata; &reference.ffi.ffi.ctype; &reference.ffi.ffi.exception; &reference.ffi.ffi.parserexception;