HHVM and Hack - Can We Expect Them to Replace PHP?

Core points

• The HHVM (HipHop Virtual Machine) and Hack programming languages ​​developed by Facebook are designed to improve the execution speed and memory efficiency of PHP. It is said that the speed is increased by 3 to 10 times and the memory usage is halved.
• Hack is an improved version of the PHP language. It is safer and more efficient. It has features such as static typing and constructor parameter improvement, reducing boilerplate code. It is fully HHVM compatible and is applied to all production servers on Facebook.
• Hack introduces collection types like Vector and Map, which have the same functionality as PHP arrays, but provides a more friendly object-oriented interface. It also supports lambda expressions, which is the abbreviation of closures.
• Hack's type system is designed to detect programming errors early and generate faster code. It is statically typed, supports scalar types, and supports generic programming, allowing for the creation of dedicated arrays and custom types.

Facebook began developing HipHop for PHP in 2008. Their goal is to speed up PHP execution, and the first version of the project consists of HPHPc/HPHPi. HPHPc is a PHP to C converter for deploying code to production servers, while HPHPi is an interpreter used during the development and debugging phases.

HPc does a great job in improving performance, but it's not without problems: keeping HPHPc and HPHPi synchronized is very cumbersome, and there are still some differences between the converted code and the explained code. That's why Facebook decided in 2010 to take another approach and created HHVM, a new virtual machine designed to replace the Zend engine used by PHP. By the end of 2012, HHVM's performance was comparable to previous HPHPc and quickly surpassed it.

HHVM is designed to achieve compatibility and optimal performance with Zend engine functions simultaneously. Facebook claims that after switching from PHP APC to HHVM, the speed has been increased by 3 to 10 times and the memory usage has been reduced by half. Of course, it really depends on the application (the 10x increase is the code base for Facebook). This article will not focus on compatibility or performance, as there are already a large number of resources available, you can check out the HHVM blog or search for "hhvm benchmark". To learn more about HipHop and HHVM, read the previous SitePoint article.

Instead, this article will focus on Hack, an improved version of the PHP language designed to improve security, performance, and development efficiency. Please note that HHVM supports both Hack and PHP. Although Hack has been used on all Facebook’s production servers, there is currently little information leaked. In short, Hack is Facebook's PHP6 - it is designed to fix most of the current PHP issues while adding some new features such as static typing.

Beginner of Hack

Not all tools and documents have been published at this time. However, the latest HHVM source code already supports Hack. You can install the Vagrant virtual machine to start experimenting with Hack and run the code snippet in this article:

<code class="language-bash"># 确保你的机器上已安装Vagrant
$ git clone https://github.com/vicb/hhvm-vagrant.git
$ cd hhvm-vagrant
$ vagrant up</code>

Now you can write your first Hack program:

<code class="language-hack"><?hh require "/vagrant/www/xhp/php-lib/init.php";

$hello = "Hello HACK!";

echo <title>{$hello}!</title>
<h1>{$hello}</h1></code>

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