Edit report at https://bugs.php.net/bug.php?id=63217&edit=1
ID: 63217
Updated by: ajf@php.net
Reported by: kmsheng at pixnet dot tw
-Summary: Behavior of implementing the ArrayAccess interface
has been changed in php 5.4
+Summary: Constant numeric strings become integers when used
as ArrayAccess offset
Status: Assigned
Type: Bug
Package: Arrays related
Operating System: freebsd
PHP Version: 5.4Git-2012-10-04 (Git)
Assigned To: ajf
Block user comment: N
Private report: N
New Comment:
I updated the title to better describe the bug.
Previous Comments:
------------------------------------------------------------------------
[2015-11-24 15:56:53] ajf@php.net
To clarify why this happens, it wasn't due to wanting to make ArrayAccess like arrays. Rather,
PHP has an optimisation for array indexing with a constant (a literal like "123", 123,
true, false, etc, not the const/define() kind) string (e.g. $_POST["password"]) where it
will check at compile-time if it is numeric and replace it then if so (so $foobar["123"]
becomes $foobar[123], but $foobar["bar"] stays the same). This means we don't have to
run the numeric string check every time that line of code is executed. Arrays in PHP consider
$foo["1"] and $foo[1] to be the same, so otherwise we'd need to check when we run the
code if the string is a number.
The problem is that $foobar in this case might actually be an object with ArrayAccess and not an
array, and so what apparently would be a transparent optimisation ends up causing this bug.
The solution is to remove this optimisation. This won't necessarily cause a performance hit,
because there's other ways we could avoid doing the numeric string check at runtime.
------------------------------------------------------------------------
[2015-11-24 15:10:48] levim@php.net
Changing this back to a bug status. Here is an example where I hope it is clear it is a bug (on
3v4l: https://3v4l.org/XGtVh):
<?php
class Dictionary implements ArrayAccess {
function offsetExists($offset) {}
function offsetGet($offset) {}
function offsetUnset($offset) {}
function offsetSet($offset, $value) {
if (!is_string($offset)) {
throw new InvalidArgumentException();
}
}
}
try {
$Dictionary = new Dictionary();
$Dictionary["12"] = 0xDEADBEEF;
echo "No Exception for \"12\"\n";
} catch (InvalidArgumentException $e) {
echo "Caught Exception for \"12\"\n";
}
try {
$str = "12";
$Dictionary[$str] = 0xDEADBEEF;
echo "No Exception for \$variable = \"12\"\n";
} catch (InvalidArgumentException $e) {
echo "Caught Exception for \$variable = \"12\"\n";
}
?>
------------------------------------------------------------------------
[2015-11-24 05:22:51] rudolf dot theunissen at gmail dot com
It makes sense for array keys to be coerced to intergers, ie. 1, 1.0, and "1" will attempt
to access the same index. However, this does not make sense for ArrayAccess. The argument for
consistency is poor, because float and object keys are handled differently already (floats stay
floats and objects don't raise warnings). One example use case is SplObjectStorage, which
makes use of object keys via ArrayAccess.
With the introduction of strict types and scalar typehints, it makes sense for the implementation to
be responsible for handling various key types.
ArrayAccess should only provide array syntax, not array behaviour.
Test script:
https://3v4l.org/0BMYh
---------------
<?php
class Test implements ArrayAccess
{
public function offsetGet($offset){
return gettype($offset);
}
public function offsetSet($offset, $value){}
public function offsetUnset($offset){}
public function offsetExists($offset){}
}
$a = array('a', 'b', 'c');
$o = new Test();
$s = '1';
echo $o[1], "\n"; // 'integer'
echo $o['1'], "\n"; // 'integer' !?
echo $o[1.0], "\n"; // 'double'
echo $o[$s], "\n"; // 'string'
echo $o[$o], "\n"; // 'object'
echo $a[1], "\n"; // 'integer'
echo $a['1'], "\n"; // 'integer'
echo $a[1.0], "\n"; // 'integer'
echo $a[$s], "\n"; // 'integer'
echo $a[$o], "\n"; // Warning: Illegal offset type
Output:
---------------
integer
integer
double
string
object
b
b
b
b
Warning: Illegal offset type in...
------------------------------------------------------------------------
[2013-04-07 17:44:34] david at grudl dot com
This is really buggy.
$test['0']; // prints int(0)
but
$key = '0';
$test[$key]; // prints string(1) "0"
------------------------------------------------------------------------
[2012-10-05 04:54:32] laruence@php.net
numeric string key will cast to number, I think this is a improvement, to be
consistent with the internal dim fetch.
but yeah, we need a document of such change, change to doc problem.
------------------------------------------------------------------------
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