PHP 8.0 is expected to be released by the end of the year, so it’s time to take a first look at the next major version of PHP. Attributes, union types, and a just-in-time compiler are likely the flagship features of this release, but there are many more improvements to be excited about. As PHP 8.0 is a major version, this release also includes backwards-incompatible changes, many of which are centered around stricter error handling and more type safety. Presentation from phpfwdays 2020.

4. Release schedule (tentative)
June 18th PHP 8.0 Alpha 1
July 28th PHP 8.0 Feature freeze
December 3rd PHP 8.0 Release

6. Just-In-Time (JIT) Compiler
●
Compiles PHP code to x86 machine code
●
Performance improvements mostly apply to
math heavy code

7. Just-In-Time (JIT) Compiler
●
Compiles PHP code to x86 machine code
●
Performance improvements mostly apply to
math heavy code
●
Part of opcache:
– opcache.jit=on
– opcache.jit_buffer_size=128M

8. Attributes
<?php
/** @Entity */
class User {
/**
* @Id
* @Column(type="integer")
* @GeneratedValue
*/
private $id;
}

9. Attributes
<?php
use DoctrineORMAttributes as ORM;
<<ORMEntity>>
class User {
<<ORMId>>
<<ORMColumn("integer")>>
<<ORMGeneratedValue>>
private $id;
}

10. Attributes
<?php
use DoctrineORMAttributes as ORM;
<<ORMEntity>>
class User {
<<ORMId>>
<<ORMColumn("integer")>>
<<ORMGeneratedValue>>
private $id;
}
Class name
Constructor arguments

11. Attributes
<?php
namespace DoctrineORMAttributes;
use PhpAttribute;
<<PhpAttribute>>
class Column {
public function __construct(string $type) { … }
}

12. Attributes
<?php
$rc = new ReflectionClass(User::class);
foreach ($rc->getAttributes() as $attr) {
var_dump($attr->getName());
// => "DoctrineORMAttributesEntity"
var_dump($attr->getArguments());
// => []
var_dump($attr->newInstance());
// object(DoctrineORMAttributesEntity) ...
}

13. Attributes
<?php
$rc = new ReflectionClass(User::class);
foreach ($rc->getAttributes() as $attr) {
var_dump($attr->getName());
// => "DoctrineORMAttributesEntity"
var_dump($attr->getArguments());
// => []
var_dump($attr->newInstance());
// object(DoctrineORMAttributesEntity) ...
}
Attribute validation happens HERE.

14. Attributes: Limitations
●
No named parameters:
– @Column(type="string", unique=true)
– <<Column("string", ['unique' => true])>>

15. Attributes: Limitations
●
No named parameters:
– @Column(type="string", unique=true)
– <<Column("string", ['unique' => true])>>
●
No nested attributes:
– @AssertAll({ @AssertNotBlank,
@AssertLength(min=5) })

16. Attributes: Limitations
●
No named parameters:
– @Column(type="string", unique=true)
– <<Column("string", ['unique' => true])>>
●
No nested attributes:
– @AssertAll({ @AssertNotBlank,
@AssertLength(min=5) })
"new" currently not supported in constant expressions

17. Attributes: Use-Cases
●
Replaces phpdoc annotations in Doctrine,
Symfony, etc…
●
May add internal attributes:
– <<Deprecated("Use xyz instead")>>
– <<Jit>>, <<NoJit>>

18. Union Types
●
Existing union types:
– ?Type = Type|null
– iterable = Traversable|array

19. Union Types
<?php
class Number {
/** @var int|float $number */
private $number;
/** @param int|float $number */
public function setNumber($number) {
$this->number = $number;
}
/** @return int|float */
public function getNumber() {
return $this->number;
}
}

20. Union Types
<?php
class Number {
private int|float $number;
public function setNumber(int|float $number) {
$this->number = $number;
}
public function getNumber(): int|float {
return $this->number;
}
}

21. Union Types
<?php
function strpos(
string $haystack, string $needle, int $offset = 0
): int|false {}

22. Union Types
<?php
function strpos(
string $haystack, string $needle, int $offset = 0
): int|false {}
Very common in standard library

23. Union Types
<?php
function strpos(
string $haystack, string $needle, int $offset = 0
): int|false {}
function array_key_first(array $arg): int|string|null {}
?Type is a shorthand for Type|null now

24. Union Types
●
Tricky interaction with "weak types"
●
Type must be part of union, or...
●
Scalars are coerced to int, float, string, bool, in
order of preference

25. Union Types
<?php declare(strict_types=0);
function test(int|float|bool $arg) {
var_dump($arg);
}
test(45); // int(45)
test(45.8); // float(45.8)
test("45"); // int(45)
test("45.8"); // float(45.8)
test(""); // bool(false)
test("X"); // bool(true)
test([]); // TypeError

26. Union Types
<?php declare(strict_types=1);
function test(int|float|bool $arg) {
var_dump($arg);
}
test(45); // int(45)
test(45.8); // float(45.8)
test("45"); // TypeError
test("45.8"); // TypeError
test(""); // TypeError
test("X"); // TypeError
test([]); // TypeError

27. Mixed Type
●
Distinguishes between:
– Type is missing because I didn't add one yet
– This function really does accept any value

28. Mixed Type
<?php
function var_dump(mixed $value, mixed ...$value): void {}
function serialize(mixed $value): string {}

29. Mixed Type
<?php
// Mixed is a common approximation for generic functions:
function array_reduce<K, V, R>(
array<K, V> $arg,
callable(R, V): R $callback, R $initial = null
): R {}

30. Mixed Type
<?php
// Mixed is a common approximation for generic functions:
function array_reduce<K, V, R>(
array<K, V> $arg,
callable(R, V): R $callback, R $initial = null
): R {}
// Back down to earth:
function array_reduce(
array $arg, callable $callback,
mixed $initial = null
): mixed {}

31. Mixed Type
<?php
// For argument types:
// No type same as mixed type
class A {
public function method(mixed $arg) {}
}
class B extends A {
public function method($arg) {}
}
Allowed

32. Mixed Type
<?php
// For return types:
// No type effectively means mixed|void
class A {
public function method(): mixed {}
}
class B extends A {
public function method() {}
}

33. Mixed Type
<?php
// For return types:
// No type effectively means mixed|void
class A {
public function method(): mixed {}
}
class B extends A {
public function method() {}
}
Forbidden: Widening return type

34. Static Return Type
<?php
// Named constructor:
class TestParent {
public function createFromWhatever($whatever): static {
return new static($whatever);
}
}

35. Static Return Type
<?php
// Named constructor:
class TestParent {
public function createFromWhatever($whatever): static {
return new static($whatever);
}
}
class TestChild extends TestParent {}
// TestChild::createFromWhatever(…)
// must return TestChild, not TestParent!

36. Static Return Type
<?php
// Wither pattern:
class Test {
public function withWhatever($whatever): static {
$clone = clone $this;
$clone->whatever = $whatever;
return $clone;
}
}

37. Static Return Type
<?php
// Fluent methods:
class Test {
public function doWhatever(): static {
// Do whatever.
return $this;
}
}

38. Constructor Promotion
<?php
class Point {
public float $x;
public float $y;
public float $z;
public function __construct(
float $x = 0.0,
float $y = 0.0,
float $z = 0.0,
) {
$this->x = $x;
$this->y = $y;
$this->z = $z;
}
}

39. Constructor Promotion
<?php
class Point {
public function __construct(
public float $x = 0.0,
public float $y = 0.0,
public float $z = 0.0,
) {}
}

40. Constructor Promotion
<?php
class Point {
public function __construct(
public float $x = 0.0,
public float $y = 0.0,
public float $z = 0.0,
) {}
}
Trailing comma in parameters lists
now allowed

41. str_contains etc.
<?php
function str_contains(
string $haystack, string $needle
): bool {
return false !== strpos($haystack, $needle);
}

42. str_contains etc.
<?php
function str_contains(
string $haystack, string $needle
): bool {}
function str_starts_with(
string $haystack, string $needle
): bool {}
function str_ends_with(
string $haystack, string $needle
): bool {}

43. str_contains etc.
●
No multibyte variants
●
All of these functions are safe to use on UTF-8!
(If you don't use UTF-8, that's your problem)

44. WeakMap
<?php
$map = new WeakMap;
$obj = new stdClass;
$map[$obj] = $dataForObj;
unset($obj); // $obj automatically dropped from WeakMap!

45. WeakMap
<?php
class FooBar {
private WeakMap $cache;
public function getSomethingWithCaching(object $obj) {
return $this->cache[$obj]
??= $this->computeSomethingExpensive($obj);
}
}

46. Backwards Compatibility Breaks
●
Everything deprecated before PHP 8.0 has
been removed!
●
Full list:
https://github.com/php/php-src/blob/master/UPGRADING

47. Resource To Object Migration
●
Long term goal: Convert all resources to objects
●
Objects are type-safe and have much better
internal support

48. Resource To Object Migration
●
Long term goal: Convert all resources to objects
●
Objects are type-safe and have much better
internal support
(This is why we do not support a "resource"
type.)

49. Resource To Object Migration
●
Usually based on "opaque objects"
●
Actual object-oriented APIs may be added later

50. Resource To Object Migration
●
Migrated in previous versions
– EnchantBroker, EnchantDictionary
– GdImage
– SysvMessageQueue
– SysvSemaphore
– XmlParser
– XmlWriter (already had an OO API)
– … more are in progress

51. Resource To Object Migration
<?php
$image = imagecreatefrompng($path);
if (!is_resource($image)) {
throw new MalformedImageException;
}

52. Resource To Object Migration
<?php
$image = imagecreatefrompng($path);
if (!is_resource($image)) {
throw new MalformedImageException;
}
Now a GdImage object on success
We'll always throw...

53. Resource To Object Migration
<?php
$image = imagecreatefrompng($path);
if (false === $image) {
throw new MalformedImageException;
}

54. Warning → Error exception
●
Many warnings converted to Error exceptions
– TypeError
– ValueError

55. Warning → Error exception
●
Only allowed for error conditions that imply
programmer error
●
It makes no sense to "handle" the error, code
needs to be fixed instead

56. Warning → Error exception
<?php
var_dump(strlen([]));
// Warning: strlen() expects parameter 1 to be string,
// array given
// NULL
function strlen(string $str): int|null {}

57. Warning → Error exception
<?php
var_dump(strlen([]));
// Uncaught TypeError: strlen(): Argument #1 ($str)
// must be of type string, array given
function strlen(string $str): int {}

58. Warning → Error exception
<?php
var_dump(array_fill(0, -100, "foobar"));
// Warning: array_fill(): Number of elements can't
// be negative
// bool(false)
function array_fill(
int $start_index, int $num, mixed $value
): array|false {}

59. Warning → Error exception
<?php
var_dump(array_fill(0, -100, "foobar"));
// Uncaught ValueError: array_fill(): Argument #2 ($num)
// must be greater than or equal to 0
function array_fill(
int $start_index, int $num, mixed $value
): array {}

60. Warning → Error exception
<?php
var_dump(fopen("does_not_exist.txt", "r"));
// Warning: fopen(does_not_exist.txt):
// Failed to open stream: No such file or directory
// bool(false)

61. Warning → Error exception
<?php
var_dump(fopen("does_not_exist.txt", "r"));
// Warning: fopen(does_not_exist.txt):
// Failed to open stream: No such file or directory
// bool(false)
NOT going to change!
fopen() failure is an environment failure condition,
it does not imply programmer error!

62. PHP Stubs
●
PHP stub files specify function signatures for
internal functions/methods
●
Used to generate C code for function
registration

63. PHP Stubs
<?php
function array_search(
mixed $needle, array $haystack, bool $strict = false
): int|string|false {}

64. PHP Stubs
<?php
function array_search(
mixed $needle, array $haystack, bool $strict = false
): int|string|false {}
ZEND_BEGIN_ARG_WITH_RETURN_TYPE_MASK_EX(
arginfo_array_search, 0, 2,
MAY_BE_LONG|MAY_BE_STRING|MAY_BE_FALSE)
ZEND_ARG_TYPE_INFO(0, needle, IS_MIXED, 0)
ZEND_ARG_TYPE_INFO(0, haystack, IS_ARRAY, 0)
ZEND_ARG_TYPE_INFO_WITH_DEFAULT_VALUE(
0, strict, _IS_BOOL, 0, "false")
ZEND_END_ARG_INFO()

65. PHP Stubs
●
Data available through Reflection:
– ReflectionFunction::getReturnType()
– ReflectionParameter::getType()
– ReflectionParameter::getDefaultValue()

66. PHP Stubs
<?php
// Stub
class DateTime implements DateTimeInterface {
/** @return DateTime */
public function add(DateInterval $interval) {}
}
// Your code
class MyDateTime extends DateTime {
public function add(DateInterval $interval) {
// Do something
}
}

67. PHP Stubs
<?php
// Stub
class DateTime implements DateTimeInterface {
/** @return DateTime */
public function add(DateInterval $interval) {}
}
// Your code
class MyDateTime extends DateTime {
public function add(DateInterval $interval) {
// Do something
}
}
Now allowed!

68. PHP Stubs
<?php
// Stub
class DateTime implements DateTimeInterface {
/** @return DateTime */
public function add(DateInterval $interval) {}
}
// Your code
class MyDateTime extends DateTime {
public function add(DateInterval $interval) {
// Do something
}
}
Now allowed!
A real return type would force all extending
classes to specify it.

70. 3v4l.org

71. Travis CI
php:
- nightly
install:
- |
if [ $TRAVIS_PHP_VERSION = 'nightly' ]; then
composer install --ignore-platform-reqs;
else
composer install;
fi
Many libraries are not formally
compatible with PHP 8 (yet)

72. Docker
●
https://github.com/devilbox/docker-php-fpm-8.0

73. Thank You!