(PHP 4, PHP 5, PHP 7) Gets the current PHP version

(PECL apc >= 3.1.1) Constructs an APCIterator iterator object

(PECL bcompiler >= 0.5) Writes a defined function as bytecodes

(PECL apd >= 0.2) Echo to the debugging socket

(PECL weakref >= 0.1.0) Checks whether the object referenced still exists

(PHP 5 >= 5.3.0, PHP 7) Activates the circular reference collector

(PECL apc >= 3.1.1) Get current item public

(PECL apc >= 3.0.0) Removes a stored variable from the cache

(PECL apc >= 3.0.0) Cache a variable in the data store

(PHP 4, PHP 5, PHP 7) Gets the value of an environment variable