[RFC] "arrayable" pseudo type hint

Since PHP 7.1, there's the "iterable" pseudo type hint that matches
"array" or "Traversable".

PHP frameworks would profit from support of an "arrayable" pseudo type
hint that matches "array" and all objects that can be used like arrays.

For that, "arrayable" objects have to implement these interfaces:

• ArrayAccess
• Countable
• Traversable (i.e. either Iterator or IteratorAggregate)

Implementing "arrayable" pseudo type, we could pass arrays or all
objects that can be used like arrays to methods and do:

function useArrayable( arrayable $arg ) : arrayable {
$cnt = count( $arg );
$value = $arg['key'];
foreach( $arg as $key => $entry );
return $arg;
}

Implementation is pretty straight forward:

https://github.com/aimeos/php-src/commit/8c4f7f1142e20696b9481f4329928a6140eb05fd

It also contains is_arrayable() and ReflectionClass::isArrayable()
methods. Tests haven't been implemented yet.

This proposal is not obsolete by the implementation of union types (i.e.
array|Traversable) because union data types are types/interfaces
combined by OR. "arrayable" is a combination of OR and AND:

array|ArrayAccess&Countable&Traversable

True. But it's also easy to implement in userland. Just create a new interface that extends these three interfaces, then union types can work.

interface Arrayable extends ArrayAccess, Countable, Traversable {}

function array_x (array|Arrayable $arr) {}

This is not something that userland cannot implement or very difficult to implement. IMO it will make php more complex if we include this in the core. Actually what you suggested has been totally covered by the future scopes of the union types RFC. If you really want to explore this idea, I think they are worth more attention, instead of this specific case.

Regards,
CHU Zhaowei

-----Original Message-----
From: Aimeos | Norbert Sendetzky norbert@aimeos.com
Sent: Wednesday, November 20, 2019 6:21 AM
To: internals@lists.php.net
Subject: [PHP-DEV] [RFC] "arrayable" pseudo type hint

Since PHP 7.1, there's the "iterable" pseudo type hint that matches "array" or
"Traversable".

PHP frameworks would profit from support of an "arrayable" pseudo type hint
that matches "array" and all objects that can be used like arrays.

For that, "arrayable" objects have to implement these interfaces:

• ArrayAccess
• Countable
• Traversable (i.e. either Iterator or IteratorAggregate)

Implementing "arrayable" pseudo type, we could pass arrays or all objects that
can be used like arrays to methods and do:

function useArrayable( arrayable $arg ) : arrayable {
$cnt = count( $arg );
$value = $arg['key'];
foreach( $arg as $key => $entry );
return $arg;
}

Best use cases are:

• Laravel Collection
  (https://github.com/laravel/framework/blob/6.x/src/Illuminate/Support/Collect
  ion.php)

• Aimeos Map (https://github.com/aimeos/map)

No new interface is proposed because we can check if objects implement:

ArrayAccess && Countable && Traversable

Because "array" !== "arrayable", "arrayable objects will not be accepted by
array_* functions and all functions that only use "array" as type hint for
parameters and return types.

This proposal is not obsolete by the implementation of union types (i.e.
array|Traversable) because union data types are types/interfaces
combined by OR. "arrayable" is a combination of OR and AND:

array|ArrayAccess&Countable&Traversable

Also, "arrayable" won't supersede "iterable" because

• "iterable" matches arrays, iterators and generators

• "arrayable" matches arrays and objects that can be used like arrays

"Can be used like arrays" doesn't include support for empty() because it works
for empty arrays but not for "arrayable" objects without elements.
If possible and requested, this may be addressed by another RFC.

As Larry Garfield suggested, this pre-RFC proposes concentrates on the
"arrayable" pseudo type only.

It does NOT discusses that:

• arrayable objects can be converted to arrays (Steven Wade works on an RFC
  for a __toArray() magic function)

• ArrayObject or any other arrayable object makes the array_* functions less
  relevant in the future

• arrayable objects can be passed to array_* functions in the future

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I would like to modify my initial concept of an "arrayable" type because
PHP core developers seems to be in favor of the upcoming union data
types instead of adding a new "arrayable" pseudo type similar to "iterable".

So, I would like to propose an "Arrayable" interface that combines
ArrayAccess, Countable and Traversable interfaces and adds a toArray()
method:

interface Arrayable extends ArrayAccess, Countable, Traversable
{
public function toArray() : array;
}

Then, methods signatures can support array and Array-like objects:

function useArrayable( array|Arrayable $arg ) : array|Arrayable {
$cnt = count( $arg );
$value = $arg['key'];
foreach( $arg as $key => $entry );
is_object( $arg ) { $nativeArray = $arg->toArray(); }
return $arg;
}

Adding a toArray() method also avoids controversy around using a magic
__toArray() method, even if this would be easier for developers in this
case.

If union data types are available and "iterable" is implemented as
alias, an alias "arrayable" for "array|Arrayable" may be added as well.

Am 19.11.19 um 23:21 schrieb Aimeos | Norbert Sendetzky:

Since PHP 7.1, there's the "iterable" pseudo type hint that matches
"array" or "Traversable".

PHP frameworks would profit from support of an "arrayable" pseudo type
hint that matches "array" and all objects that can be used like arrays.

For that, "arrayable" objects have to implement these interfaces:

• ArrayAccess
• Countable
• Traversable (i.e. either Iterator or IteratorAggregate)

Implementing "arrayable" pseudo type, we could pass arrays or all
objects that can be used like arrays to methods and do:

function useArrayable( arrayable $arg ) : arrayable {
$cnt = count( $arg );
$value = $arg['key'];
foreach( $arg as $key => $entry );
return $arg;
}

Best use cases are:

• Laravel Collection
  (https://github.com/laravel/framework/blob/6.x/src/Illuminate/Support/Collection.php)

• Aimeos Map (https://github.com/aimeos/map)

No new interface is proposed because we can check if objects implement:

ArrayAccess && Countable && Traversable

Because "array" !== "arrayable", "arrayable objects will not be accepted
by array_* functions and all functions that only use "array" as type
hint for parameters and return types.

This proposal is not obsolete by the implementation of union types (i.e.
array|Traversable) because union data types are types/interfaces
combined by OR. "arrayable" is a combination of OR and AND:

array|ArrayAccess&Countable&Traversable

Also, "arrayable" won't supersede "iterable" because

• "iterable" matches arrays, iterators and generators

• "arrayable" matches arrays and objects that can be used like arrays

"Can be used like arrays" doesn't include support for empty() because it
works for empty arrays but not for "arrayable" objects without elements.
If possible and requested, this may be addressed by another RFC.

As Larry Garfield suggested, this pre-RFC proposes concentrates on the
"arrayable" pseudo type only.

It does NOT discusses that:

• arrayable objects can be converted to arrays (Steven Wade works on an
  RFC for a __toArray() magic function)

• ArrayObject or any other arrayable object makes the array_* functions
  less relevant in the future

• arrayable objects can be passed to array_* functions in the future