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

(PECL runkit >= 0.7.0) Runkit Sandbox Class -- PHP Virtual Machine

(PECL apcu >= 5.1.0) Atomically fetch or generate a cache entry

(PECL apc >= 3.1.4) Load a binary dump into the APC file/user cache

(PECL weakref >= 0.2.0) Advances to the next map element

(PHP 5, PHP 7) Prints a backtrace void debug_print_backtrace

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

(PHP 4, PHP 5, PHP 7) Returns an array with the names of all modules compiled and loaded

(PHP 5, PHP 7) Restores the previously defined exception handler function

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