PHP 8.1: key(), current(), next(), prev(), reset() and end() on \stdClass should not be deprecated

[MircoBabin]

Description

The following code:

<?php

// Laravel 9 / Eloquent: DB::getSchemaBuilder()->getAllTables()
//     Executes MySql query: SHOW FULL TABLES WHERE table_type = 'BASE TABLE'
//     Returns an array of \stdClass objects using PDO.
//
// The problem is that the name of the first column is databasename dependent 'Tables_in_'+databasename. 
// e.g. If the databasename is 'tripportal' the first columnname will be 'Tables_in_tripportal'.
// Retrieving the first column value is cumbersome, because it has not a fixed name.

// https://wiki.php.net/rfc/deprecations_php_8_1
// * key(), current(), next(), prev(), and reset() on objects

function startTest($name, $func)
{
    echo PHP_EOL;
    echo '------------------------------------------------------------------------------'.PHP_EOL;
    
    echo '[BEGIN] '.$name.PHP_EOL;
    
    $func();
    
    echo '[END] '.$name.PHP_EOL;
}


$row = new \stdClass();
$row->Tables_in_tripportal = 'users';
$row->Table_type = 'BASE TABLE';

startTest('foreach', function () use ($row) {
    foreach($row as $columnName => $value) {
        echo $columnName.' => '.$value.PHP_EOL;
    }
});

startTest('key', function () use ($row) {
    $firstColumnName = key($row);
    echo $firstColumnName.PHP_EOL;
});

startTest('current', function () use ($row) {
    $firstColumnValue = current($row);
    echo $firstColumnValue.PHP_EOL;
});

startTest('reset', function () use ($row) {
    $firstColumnValue = reset($row);
    echo $firstColumnValue.PHP_EOL;
});

startTest('next', function () use ($row) {
    $firstColumnValue = reset($row);
    $secondColumnValue = next($row);
    echo $secondColumnValue.PHP_EOL;
});

startTest('end', function () use ($row) {
    $secondColumnValue = end($row);
    echo $secondColumnValue.PHP_EOL;
});

startTest('prev', function () use ($row) {
    $secondColumnValue = end($row);
    $firstColumnValue = prev($row);
    echo $firstColumnValue.PHP_EOL;
});

startTest('reset(array)', function () use ($row) {
    $firstColumnValue = reset((array)$row);
    echo $firstColumnValue.PHP_EOL;
});

Resulted in this output:

------------------------------------------------------------------------------
[BEGIN] foreach
Tables_in_tripportal => users
Table_type => BASE TABLE
[END] foreach

------------------------------------------------------------------------------
[BEGIN] key

Deprecated: key(): Calling key() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 38
Tables_in_tripportal
[END] key

------------------------------------------------------------------------------
[BEGIN] current

Deprecated: current(): Calling current() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 43
users
[END] current

------------------------------------------------------------------------------
[BEGIN] reset

Deprecated: reset(): Calling reset() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 48
users
[END] reset

------------------------------------------------------------------------------
[BEGIN] next

Deprecated: reset(): Calling reset() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 53

Deprecated: next(): Calling next() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 54
BASE TABLE
[END] next

------------------------------------------------------------------------------
[BEGIN] end

Deprecated: end(): Calling end() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 59
BASE TABLE
[END] end

------------------------------------------------------------------------------
[BEGIN] prev

Deprecated: end(): Calling end() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 64

Deprecated: prev(): Calling prev() on an object is deprecated in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 65
users
[END] prev

------------------------------------------------------------------------------
[BEGIN] reset(array)

Fatal error: Uncaught Error: reset(): Argument #1 ($array) cannot be passed by reference in D:\Projects\Webpage\tripportals\testStdClassAsArray.php:70
Stack trace:
#0 D:\Projects\Webpage\tripportals\testStdClassAsArray.php(21): {closure}()
#1 D:\Projects\Webpage\tripportals\testStdClassAsArray.php(72): startTest('reset(array)', Object(Closure))
#2 {main}
  thrown in D:\Projects\Webpage\tripportals\testStdClassAsArray.php on line 70

But I expected this output instead:

No deprecation warnings about calling key(), current(), reset(), next(), end(), prev() on an object is deprecated.

---

I can't understand why the RFC deprecations 8.1 has not taken \stdClass into account. I believe \stdClass should be an exception. Because \stdClass and array are positioned throughout the documentation as interchangable. It is easy to cast from array to \stdClass and vice versa. And Laravel 9 with Eloquent is using \stdClass when not using models for querying the MySql database.

I had this code:

<?php
$table_name = reset($row);

And now I have to change this to:

<?php
$table_name = current((array) $row);

// NOTE: the RFC presented below alternative. But this just gives a Fatal error.
// $table_name = reset((array) $row);
// Fatal error: Uncaught Error: reset(): Argument #1 ($array) cannot be passed by reference in D:\Projects\Webpage\tripportals\testStdClassAsArray.php:70

I don't see this as an approvement of the language. Note, I'm only talking about \stdClass, not about other objects.

The RFC states:

As such, the proposal is to deprecate key(), current(), next(), prev() and reset() on objects. The suggested replacement is to cast the object to array first, or call get_mangled_object_vars(), depending on what the intention is.

But this is a false assumption, because reset((array) $row); gives a Fatal error: Uncaught Error: reset(): Argument #1 ($array) cannot be passed by reference.

PHP Version

PHP 8.1.4

Operating System

Windows/10

[damianwadley]

The basic premise of the deprecation is that key/current/next/prev/reset are about dealing with arrays. The fact that they worked on objects was somewhat accidental and due to PHP's implementation of objects. The deprecation is the first step in reaching the standard behavior of array functions working on arrays.

If you'd like to talk more about this, the internals mailing list is the more appropriate place.
https://www.php.net/mailing-lists.php

Because \stdClass and array are positioned throughout the documentation as interchangable.

No? Objects and arrays are not interchangeable. Even when implementing ArrayAccess there are still significant differences.

Note, I'm only talking about \stdClass, not about other objects.

Creating a special exception for stdClass is going to create even more confusion: "why can I use reset() on this object but I can't use it on this other object?"

But this is a false assumption,

Obviously you'd need to do the cast as a separate statement.

$array = (array) $row;
// now pass $array everywhere that you expect an array
reset($array)

[MircoBabin]

@damianwadley thanks for inviting me to internals mailing list. But I'm not going to accept the invitation. If a discussion is wanted with me, this Github issue is the place to discuss it.

---

No? Objects and arrays are not interchangeable. Even when implementing ArrayAccess there are still significant differences.

At a mental level \stdClass and array are interchangable. It's just other syntactic sugar, where array is the "old" style and stdClass is the "oop" style. Again I note that I'm not talking about objects but only about \stdClass.

I have found the following searching php.net.

1. https://www.php.net/manual/en/function.var-export.php
   PHP 7.3.0 Now exports stdClass objects as an array cast to an object ((object) array( ... )), rather than using the nonexistent method stdClass::__setState(). The practical effect is that now stdClass is exportable, and the resulting code will even work on earlier versions of PHP.

2. https://wiki.php.net/rfc/iterable-stdclass
   By far the most common usage of stdClass is (as the manual defines) “Created by typecasting to object”, or from the result of a call to 'json_decode()' using the default parameters. In both of these scenarios the resulting object is analogous to a plain array. Although it is a class, it has no methods or private/protected properties, it is simply an array that uses a different syntax for accessing its elements.

3. https://wiki.php.net/rfc/deprecate_dynamic_properties
   When writing to a property that has not been declared, PHP will silently create a dynamic property instead. In modern code, this is rarely done intentionally. This RFC proposes to deprecate and later remove the creation of dynamic properties, unless the class explicitly allows dynamic properties. stdClass and __get/__set are not affected by this change.

---

Creating a special exception for stdClass is going to create even more confusion: "why can I use reset() on this object but I can't use it on this other object?"

Obviously you'd need to do the cast as a separate statement.

$array = (array) $row;
// now pass $array everywhere that you expect an array
reset($array)

I know this can be a solution, although it is a very ugly one. And that was the reason why I opened this bug. I really don't see this as an improvement, the mandatory introduction of a new variable to make the reset() work. Or my solution to use current((array) $row);.

And other RFC's like https://wiki.php.net/rfc/deprecate_dynamic_properties do take \stdClass into account as a special object. So in my opinion \stdClass should never be shared under the generic group of objects. And should always be considered special.