Hack the Future

Hack the Future
Jason McCreary
"JMac"
@gonedark

Hack the Future - Jason McCreary - php[world] 2015
Talk the Talk
1. What is Hack?
2. Key Features of Hack
3. Unsupported PHP features in Hack
4. How can I use Hack?
5. Why Hack?
6. The Future
2

But ﬁrst…
A quick disclaimer.
3

"Some things are going to be said."
4

"This is not a talk to push Hack."
5

"This is not a talk to shit on PHP."
6

"This is a talk about the evolution of a language."
7

What is Hack?
A very brief history.
8

Brief History
• In 2009, Facebook released HipHop - a PHP compiler
• In 2010, Facebook introduced new features into PHP
• In 2012, Facebook began working on Hack
• In 2013, Facebook released HHVM - a HipHopVM
• In 2014, Facebook released Hack
9

So what is Hack?
"Hack is a programming language for HHVM that
interoperates seamlessly with PHP."
10

So what is Hack, really?
"Hack is a superset of PHP that runs on HHVM which
provides type checking."
11

WTF Facebook?
Just use PHP.
12

"Well, they do."
13

"Facebook has millions of lines of PHP."
14

"Instead of a rewrite or waiting or inﬂuencing the PHP
community, they made Hack."
15

"The goal being to write cleaner, safer, and
refactorable code."
16

Key Features
A deeper look at some of the features of Hack.
17

Key Features in Hack
• Type Annotations
• Additional types
• Generics and Nullable
• Asynchronous programming
• Syntactic sugar
18

Type Annotations
<?hh 
// parameter type annotations
function output(string $str) {
echo 'Hello, ' . $str;
}
// return type annotations
function get_output(string $str): string {
return 'Hello, ' . $str;
}
19

"Hack is not a statically typed language."
20

"Hack allows more type hinting than PHP."
21

"HHVM performs type checking before runtime which
ensures your code is type safe."
22

Additional Types
• Collections
• Enums
• Shapes
• Tuples
• Custom Types
23

The problem with array
"In PHP, arrays are used for all the things!"
24

<?php
// indexed, starting at 0
$arr1 = array(1, 2, 3);
// indexed, starting at 1
$arr2 = array(1 => 1, 2, 3);
// keyed, mix of integer keys and string keys
$arr3 = array("foo" => 1, 73 => 2, "bar" => 3);
// all array values are the same
26

"Primitive obsession is a code smell!"
27

"In PHP, arrays are primitives (i.e. non-objects)."
28

$ php -r 'var_dump(is_object(array()));'
bool(false)
29

Collections
• Vector - an ordered, index collection
• Map - a key-based collection
• Set - an unordered, uniquely value collection
• Pair - an immutable, indexed, 2 element collection
• Both immutable and mutable versions
30

Collections
<?hh
 
$vector = Vector {5, 10, 15};
$map = Map {"A" => 1, "B" => 2, "C" => 3};
$set = Set {"A", "B"};
31

Enums
<?hh
enum DayOfWeek: int {
Sunday = 0;
Monday = 1;
Tuesday = 2;
Wednesday = 3;
Thursday = 4;
Friday = 5;
Saturday = 6;
}
echo DayOfWeek::Wednesday; // outputs 3
32

Shapes
<?hh
// fixed size and type
// keyed collection of mixed values
$sh = shape('x' => 3, 'y' => 5);
echo $sh['x'] . ',' . $sh['y']; // outputs 3,5
33

Tuples
<?hh
// fixed size and type, index array of mixed values
$tup = tuple('3', 2, 3, 4, 'hi');
echo $tup[1]; // outputs 2
unset($tup[0]); // error
$tup[5] = 'new value'; // error
$tup[4] = 'change value'; // ok, string to string
34

Custom Types
<?hh 
// define your own types
type MyInt = int;
type Point = (int, int);
35

Generics and Nullable
• Generics - ability to parameterize the type of a class
or method and declare it upon instantiation
• Nullable - ability to declare a type allows null
36

Generics
<?hh
class Box<T> {
protected T $data;
public function __construct(T $data) {
$this->data = $data;
}
public function getData(): T {
return $this->data;
}
}
37

Nullable
<?hh
function check_not_null(?int $x): int {
if ($x === null) {
return -1;
} else {
return $x;
}
}
38

Asynchronous Programming
<?hh
async function helloAfter($name, $timeout): Awaitable<string> {
await SleepWaitHandle::create($timeout * 1000000);
echo sprintf("hello %sn", $name);
}
async function run() {
$joe = helloAfter('Joe', 3);
$mike = helloAfter('Mike', 1);
await GenArrayWaitHandle::create(array($joe, $mike));
}
run()->join();
// prints:
// hello Mike
// hello Joe
39

Syntactic Sugar
• Constructor Argument Promotion
• Lambdas
40

Constructor Argument Promotion
<?php
class Person {
private string $name;
private int $age;
public function __construct(string $name, int $age) {
$this->name = $name;
$this->age = $age;
}
}
41

Constructor Argument Promotion
<?hh
class Person {
public function __construct(public string $name,
protected int $age) {}
}
42

Lambdas
<?php
$foo = function($x) {
return $x + 1;
}
$foo(12); // returns 13
$squared = array_map(function($x) {
return $x * $x;
}, array(1,2,3));
var_dump($squared); // $squared is array(1,4,9)
43

Lambdas
<?hh
$foo = $x ==> $x + 1;
$foo(12); // returns 13
$squared = array_map($x ==> $x * $x, array(1,2,3));
var_dump($squared); // $squared is array(1,4,9)
44

Unsupported PHP Features
The things Hack no likey.
45

Unsupported PHP Features
• Alternative syntaxes: AND, OR, XOR, endif, etc.
• Dynamic features: eval, continue n, break n, 
$$var, $obj->{$var}
• Top Level Code
• References
• Globals
• Case insensitive function calls
• Explicitly named constructors
46

How can I use Hack?
What you need to do to start Hack’in.
47

"Change <?php to <?hh"
48

"You’re right, ﬁrst install HHVM."
49

"Then change <?php to <?hh!"
50

Hack Modes
• Hack has three modes: strict, partial, and
decl
• strict - type checker will catch every type error
• partial - type checker checks code that uses types
• decl - allows strict code to call separate, legacy
code
• The default is partial
51

Hack Modes
<?hh // strict
function example(int $x) {
echo "I'm so strict!";
}
52

Why Hack?
Some reasons for using Hack.
53

Reasons to Hack
• Code clarity
• Performance
• Language features, like Asynchronous Programming
• Evolution
54

The Future
So bright, I gotta wear shades.
55

Some things in PHP
• Variadic functions (PHP 5.6)
• Scalar type declarations (PHP 7)
• Return type declarations (PHP 7)
• Null coalesce operator (PHP 7)
• Deprecations: alternative syntax and named
constructors (PHP 7)
56

Look familiar?
<?php
function add(int $x, int $y): int {
return $x + $y;
}
$nil = null;
$foo = $nil ?? add(2, 3);
57

"Yeah, Hack had it ﬁrst."
58

"Hack, coming soon in PHP 7+."
59

"This is evolution."
60

Questions…
Ask now or tweet me @gonedark.
61

Hack the Future

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