LXXXIII. POSIX Functions
This module contains an interface to those functions defined in the IEEE 1003.1 (POSIX.1) standards document which are not accessible through other means. POSIX.1 for example defined the open(), read(), write() and close() functions, too, which traditionally have been part of PHP 3 for a long time. Some more system specific functions have not been available before, though, and this module tries to remedy this by providing easy access to these functions.
POSIX functions are enabled by default. You can disable POSIX-like functions with --disable-posix.
The section about Process Control Functions maybe of interest for you.