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Posted by Schraalhans Keukenmeester on 04/03/07 00:17
rick@fourfront.ltd.uk wrote:
> I have a situation where I want to write an extensible class that is
> capable of saving / restoring properties of classes derived from it.
> A simplified example is explained as follows;-
>
> class A
> {
> private $Save ;
>
> public function Push()
> {
> $this->Save = serialize( get_object_vars( $this ) ) ;
> }
>
> public function Pop()
> {
> foreach( unserialize( $this->Save ) as $Prop => $Value )
> $this->$Prop = $Value ;
> }
> }
>
> class B extends A
> {
> private $Priv ;
>
> public function SetPriv( $Num )
> {
> $this->Priv = $Num ;
> }
>
> public function GetPriv()
> {
> return $this->Priv ;
> }
> }
>
> $C = new B ;
> $C->SetPriv( 1 ) ;
> $C->Push() ;
> $C->SetPriv( 2 ) ;
> echo $C->GetPriv()."<br/>\n" ;
> $C->Pop() ;
> echo $C->GetPriv()."<br/>\n" ;
>
> At the point of the call to $C->Pop(), I get the following error;-
>
> Cannot access private property B::$Priv
>
> It is only private properties which cause this problem, public and
> protected properties defined in B will save and restore as intended.
>
> Is there a way around this ?
> TIA
>
If keeping the variable shielded from client code is most important to
you in this particular case, consider leaving them public, write a
custom __get() and __set() accessors and catch attempts at meddling with
$priv there. Not completely 'as it should' but it does the job.
Or define the (protected) variable in the parent class instead and
access it through parent::$priv.
I know protected vars in the parent class ARE visible to its children,
but I haven't got a clue whether this also goes the other way around.
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