Hack
A team of Facebook software engineers has developed a new programming language, dubbed Hack, that's intended to allow for fast changes and minimal glitches.

Hack has already been deployed at Facebook, with the social network migrating "nearly our entire PHP codebase to Hack" over the last year, engineer Julien Verlaguet said in a blog post.
But now it's your turn to try it out, as Facebook today launched an open-source version of Hack.
What's the big deal? As Verlaguet explained, programmers often encounter tasks on a day-to-day basis that can be "tricky or cumbersome." Sometimes this causes problems that aren't caught until much later, slowing down the process.
"At Facebook scale — with thousands of engineers shipping new code twice a day — slowdowns like these are even more problematic," Verlaguet wrote.
Ultimately, engineers had a choice - move quickly but sacrifice the ability to catch errors early or use statically typed languages at the cost of quick iteration.
"We believed there had to be a sweet spot," Verlaguet said. "Thus, Hack was born. We believe that it offers the best of both dynamically typed and statically typed languages, and that it will be valuable to projects of all sizes."
Over time, Verlaguet and the team wants to "evolve this software to make development even easier for both our own engineers and the broader community." He stressed that Hack should not be limited to large, Facebook-level projects; "with type information, good error messages, and fast feedback, small codebases can reap the benefits of Hack as well," he wrote.
Next month, the team will introduce the language at the Hack Developer Day on the Facebook campus in Menlo Park; "We would love to have your feedback on our work so far, and welcome you all to participate in the HHVM and Hack community."