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Fix GH-21687: array_walk creates references to readonly properties #21690

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Fix GH-21687: array_walk creates references to readonly properties #21690

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32 changes: 32 additions & 0 deletions Zend/tests/gh21687.phpt
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Original file line number Diff line number Diff line change
@@ -0,0 +1,32 @@
--TEST--
GH-21687 (array_walk corrupts readonly and enum properties by wrapping them in IS_REFERENCE)
--FILE--
<?php
enum Foo: int {
case Bar = 0;
}

$bar = Foo::Bar;
try {
array_walk($bar, function($v) {});
} catch (\Error $e) {
echo $e->getMessage() . "\n";
}
var_dump($bar);

class MyObj {
public function __construct(public readonly string $name = "test") {}
}
$obj = new MyObj();
try {
array_walk($obj, function(&$v) { $v = "modified"; });
} catch (\Error $e) {
echo $e->getMessage() . "\n";
}
echo $obj->name . "\n";
?>
--EXPECT--
Cannot acquire reference to readonly property Foo::$name
enum(Foo::Bar)
Cannot acquire reference to readonly property MyObj::$name
test
15 changes: 12 additions & 3 deletions ext/standard/array.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1409,10 +1409,19 @@ static zend_result php_array_walk(
/* Add type source for property references. */
if (Z_TYPE_P(zv) != IS_REFERENCE && Z_TYPE_P(array) == IS_OBJECT) {
zend_property_info *prop_info =
zend_get_typed_property_info_for_slot(Z_OBJ_P(array), zv);
zend_get_property_info_for_slot(Z_OBJ_P(array), zv);
if (prop_info) {
ZVAL_NEW_REF(zv, zv);
ZEND_REF_ADD_TYPE_SOURCE(Z_REF_P(zv), prop_info);
if (UNEXPECTED(prop_info->flags & ZEND_ACC_READONLY)) {
zend_throw_error(NULL,
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@ndossche ndossche Apr 9, 2026

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I think the canonical message is Cannot indirectly modify readonly property Foo::$prop

E.g. from:

<?php

class Foo {
    public readonly int $prop;
    public function __construct() {
        $this->prop = 1;
    }
}

$foo = new Foo;
$ref =& $foo->prop;

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@iliaal iliaal Apr 9, 2026

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foreach by-ref uses "Cannot acquire reference to readonly property", direct $ref =& $foo->prop uses "Cannot indirectly modify readonly property."

 class Foo {
      public readonly int $prop;
      public function __construct() { $this->prop = 1; }
  }
  $foo = new Foo;
  foreach ($foo as &$v) {}
  // Error: Cannot acquire reference to readonly property Foo::$prop

I matched the foreach wording since array_walk iterates properties and both are array related, but "Cannot indirectly modify" works too. @ndossche I can update the message, if you prefer, but there is a bit of inconsistency here

"Cannot acquire reference to readonly property %s::$%s",
ZSTR_VAL(prop_info->ce->name),
zend_get_unmangled_property_name(prop_info->name));
break;
}
if (ZEND_TYPE_IS_SET(prop_info->type)) {
ZVAL_NEW_REF(zv, zv);
ZEND_REF_ADD_TYPE_SOURCE(Z_REF_P(zv), prop_info);
}
}
}
}
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