(PECL weakref >= 0.1.0) Releases a previously acquired reference

(PHP 4, PHP 5, PHP 7) Gets the version of the current Zend engine

(PHP 4, PHP 5, PHP 7) Sets the value of a configuration option

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

(PHP 5 >= 5.5.5, PHP 7, PECL ZendOpcache > 7.0.2) Get status information about the cache

(PECL bcompiler >= 0.4) Writes the single character \x00 to indicate End of compiled data

(PECL apcu >= 4.0.0) Cache a variable in the data store

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

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

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