From: php at tjworld dot net
Operating system: Windows 2003
PHP version: 5.0.5
PHP Bug Type: Class/Object related
Bug description: __set() and read-only property prevents proper Class
inheritence
Description:
------------
When extending a class that has a visible (public or protected) read-only
dynamic property by virtue of __set(), the sub-class is prevented from
modifying (or "overloading") the property as if it were merely a public
consumer of an instance-object of super, rather than an extension of the
class definition itself.
This shows up in particular in the DOM classes DOMNode and DOMDocument,
where it causes:
Fatal error: extDOMElement::__construct() [function.--construct]: Cannot
write property in...
If you extend both classes, and try to create a new derived extDOMNode
object using a custom extDOMDocument->createElement(), it is impossible
to set any of the new extDOMNode's dynamic properties from within
extDOMNode's constructor (especially ownerDocument) because DOMNodes
without an owner are forced to be read-only.
The extDOMNode class definition should be able to modify the publically
visible ownerDocument property.
Since real properties accessible from a sub-class can't be private (if
they're to be accessible from other objects), it follows that the same
rule should apply to dynamic properties. If this were so the dynamic
properties made visible by __set() would be inherited as protected or
public and this issue wouldn't arise.
Reproduce code:
---------------
class ReadOnly {
protected $realProperty;
private $dynamicProperty = array();
function __construct() {
$realProperty = 12;
$this->members['test'] = 'read-only';
}
public function __set($name, $value) {
if($name=='test') {
if(isset($this->dynamicProperty[$name]))
throw new Exception("Can't overwrite $name");
$props[$name] = $value;
}
}
}
class Writeable extends ReadOnly {
function __construct($value) {
parent::__construct();
$this->realProperty = 25; // ok
$this->test = $value; // causes Fatal Error
}
}
$test = new Writeable('write to me');
Expected result:
----------------
The extended class should be able to inherit and modify protected or
public properties of the super class.
Actual result:
--------------
For built-in classes causes a Fatal Error. For user defined classes causes
a user-defined read-only result. In the example causes an Exception.
--
Edit bug report at http://bugs.php.net/?id=35104&edit=1
--
Try a CVS snapshot (php4): http://bugs.php.net/fix.php?id=35104&r=trysnapshot4
Try a CVS snapshot (php5.0):
http://bugs.php.net/fix.php?id=35104&r=trysnapshot50
Try a CVS snapshot (php5.1):
http://bugs.php.net/fix.php?id=35104&r=trysnapshot51
Fixed in CVS: http://bugs.php.net/fix.php?id=35104&r=fixedcvs
Fixed in release: http://bugs.php.net/fix.php?id=35104&r=alreadyfixed
Need backtrace: http://bugs.php.net/fix.php?id=35104&r=needtrace
Need Reproduce Script: http://bugs.php.net/fix.php?id=35104&r=needscript
Try newer version: http://bugs.php.net/fix.php?id=35104&r=oldversion
Not developer issue: http://bugs.php.net/fix.php?id=35104&r=support
Expected behavior: http://bugs.php.net/fix.php?id=35104&r=notwrong
Not enough info:
http://bugs.php.net/fix.php?id=35104&r=notenoughinfo
Submitted twice:
http://bugs.php.net/fix.php?id=35104&r=submittedtwice
register_globals: http://bugs.php.net/fix.php?id=35104&r=globals
PHP 3 support discontinued: http://bugs.php.net/fix.php?id=35104&r=php3
Daylight Savings: http://bugs.php.net/fix.php?id=35104&r=dst
IIS Stability: http://bugs.php.net/fix.php?id=35104&r=isapi
Install GNU Sed: http://bugs.php.net/fix.php?id=35104&r=gnused
Floating point limitations: http://bugs.php.net/fix.php?id=35104&r=float
No Zend Extensions: http://bugs.php.net/fix.php?id=35104&r=nozend
MySQL Configuration Error: http://bugs.php.net/fix.php?id=35104&r=mysqlcfg
