Under what circumstances is it possible that parent fields are not inherited?

Question

I've got a curious bug (bugging me) today. There are three inheritance levels involved:

Grandpa:

abstract class Zend_Db_Table_Row_Abstract implements ArrayAccess, 
                                                     IteratorAggregate
{
    protected $_data = array();

    /* snip */
}

Mom:

namespace Survey\Db\Table\Row;

class AbstractRow extends \Zend_Db_Table_Row_Abstract
{
    /* snip */
}

Child:

namespace Survey\Db\Table\Row;

class SurveyItem extends AbstractRow implements ISkippable
{
    /* snip */
}

Exception:

Type:     ErrorException  
Value:    Undefined property: Survey\Db\Table\Row\SurveyItem::$_data  
Location: [...]/Zend/Db/Table/Row/Abstract.php in handleError , line 177  

Line 177 doesn't seem to be relevant, but I'm adding it just so you'd believe me ;)

if (!array_key_exists($columnName, $this->_data)) {

PHP 5.4.11, problem did NOT exist with PHP 5.4.8

When I saw the fix for Bug #63462 Magic methods called twice for unset protected properties, I thought, that wold solve the problem, since this bug leads to exactly the weird unexpected outcome I was seeing.

But it turns out, the problem still exists after updating to PHP 5.4.12. The likelyhood that there is another similar bug in PHP seems quite high.

Question:

I get the info that a protected field defined in the Grandpa is undefined in the Child. What scenarios can lead to such an outcome?

Answer 1

following snippet works flawlessly on PHP 5.4.9:

class A
{
    protected $foo = 'hello';
    public function bar()
    {
        echo $this->foo;
    }
}

class B extends A {}

class C extends B {}

$c = new C();
$c->bar();

Please minimise your code step by step to this to see if/when problem occurs (I wonder why you haven't done it already)

If you are sure this worked on PHP 5.4.8 and does not work on PHP 5.4.11 then you found a bug in PHP and should be reporting it on php.net

Answer may be different (maybe it simply got 'unset' along the way). Minimise your code and you will know.