WHAT IS LIBPHUTIL?

libphutil is a collection of utility classes and functions for PHP. Some
features of the library include:

libphutil Library System
  A system for organizing, loading and introspecting PHP classes and functions.
  Uses static analysis to generate, validate and update library contents and
  includes. Based on Facebook's similar 'flib' system.

Futures
  Futures (also known as "promises") are objects which act as placeholders for
  some future result of computation. They let you express parallel and
  asynchronous execution with a natural syntax. There are two provided concrete
  Future implementations: ExecFuture for executing system commands, and
  HTTPFuture for making HTTP requests.

Filesystem
  The builtin PHP filesystem functions return error codes and emit warnings.
  It is tedious to check these consistently. The Filesystem class provides a
  simple API for common filesystem operations that throws exceptions on failure.

xsprintf
  This module allows you to build sprintf()-style functions that have arbitrary
  conversions. This is particularly useful for escaping data correctly. Three
  concrete implementations are provided:
    csprintf(): safely escape data for system commands
    jsprintf(): safely escape data for Javascript
    qsprintf(): safely escape data for MySQL (in Phabricator)

AAST/PHPAST
  An abstract, abstract syntax tree which can make it easier to perform simple
  static analysis, and a concrete AST for PHP.

Remarkup
  A Markdown-like lightweight markup language. Remarkup's syntax is defined by
  parser plugins and fairly easy to extend and configure.

Daemons
  Enables running PHP scripts as stable, long-lived daemons.

Utilities
  A handful of solid utility functions.

libphutil is used by Phabricator, Arcanist and Diviner.