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Subject Author Date
Overriding class constants Gordon 07-03-2008
Posted by Gordon on July 3, 2008, 9:18 am
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 I want to provide a set of static functions in a superclass that work
with class constants defined in a decendant of that class.
Unfortunately I've run into a snag with this idea. Example:

class SuperClass
{
        const CNST        = 'Super class';

        public static function getCnst ()
        {
                return self::CNST;
        }
}

class SubClass extends SuperClass
{
        const CNST        = 'Sub class';
}

echo (SubClass::getCnst ());

I'd want the above code tou output "Sub Class", but instead it outputs
"Super class".

It would sem that static functions can't work with overridden
constants in subclasses, or am I missing something?

Posted by Jerry Stuckle on July 3, 2008, 11:25 am
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 Gordon wrote:
> I want to provide a set of static functions in a superclass that work
> with class constants defined in a decendant of that class.
> Unfortunately I've run into a snag with this idea. Example:
>
> class SuperClass
> {
>         const CNST        = 'Super class';
>
>         public static function getCnst ()
>         {
>                 return self::CNST;
>         }
> }
>
> class SubClass extends SuperClass
> {
>         const CNST        = 'Sub class';
> }
>
> echo (SubClass::getCnst ());
>
> I'd want the above code tou output "Sub Class", but instead it outputs
> "Super class".
>
> It would sem that static functions can't work with overridden
> constants in subclasses, or am I missing something?
>

Nope, unfortunately, this is true.

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==================
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Jerry Stuckle
JDS Computer Training Corp.
jstucklex@attglobal.net
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Posted by Michael Fesser on July 3, 2008, 11:29 am
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.oO(Gordon)

>I want to provide a set of static functions in a superclass that work
>with class constants defined in a decendant of that class.
>Unfortunately I've run into a snag with this idea. Example:
>
>class SuperClass
>{
>        const CNST        = 'Super class';
>
>        public static function getCnst ()
>        {
>                return self::CNST;
>        }
>}
>
>class SubClass extends SuperClass
>{
>        const CNST        = 'Sub class';
>}
>
>echo (SubClass::getCnst ());
>
>I'd want the above code tou output "Sub Class", but instead it outputs
>"Super class".
>
>It would sem that static functions can't work with overridden
>constants in subclasses, or am I missing something?

Currently static references are resolved at compile time. What you need
here is called late static binding and scheduled for PHP 5.3.

Micha

Posted by Gordon on July 4, 2008, 4:14 am
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> .oO(Gordon)
>
>
>
> >I want to provide a set of static functions in a superclass that work
> >with class constants defined in a decendant of that class.
> >Unfortunately I've run into a snag with this idea. Example:
>
> >class SuperClass
> >{
> > const CNST = 'Super class';
>
> > public static function getCnst ()
> > {
> > return self::CNST;
> > }
> >}
>
> >class SubClass extends SuperClass
> >{
> > const CNST = 'Sub class';
> >}
>
> >echo (SubClass::getCnst ());
>
> >I'd want the above code tou output "Sub Class", but instead it outputs
> >"Super class".
>
> >It would sem that static functions can't work with overridden
> >constants in subclasses, or am I missing something?
>
> Currently static references are resolved at compile time. What you need
> here is called late static binding and scheduled for PHP 5.3.
>
> Micha

Thanks.

Is there any kind of a workaround possible in older versions? The
only way I've found to get it to work as intended is to "inherit from
the clipboard" and cut and paste the methods into all the classes.
Maintainence nightmare.

Posted by Mathieu Maes on July 4, 2008, 4:50 am
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>
>
>
> > .oO(Gordon)
>
> > >I want to provide a set of static functions in a superclass that work
> > >with class constants defined in a decendant of that class.
> > >Unfortunately I've run into a snag with this idea. =A0Example:
>
> > >class SuperClass
> > >{
> > > =A0 =A0const CNST =A0 =A0 =A0=3D 'Super class';
>
> > > =A0 =A0public static function getCnst ()
> > > =A0 =A0{
> > > =A0 =A0 =A0 =A0 =A0 =A0return self::CNST;
> > > =A0 =A0}
> > >}
>
> > >class SubClass extends SuperClass
> > >{
> > > =A0 =A0const CNST =A0 =A0 =A0=3D 'Sub class';
> > >}
>
> > >echo (SubClass::getCnst ());
>
> > >I'd want the above code tou output "Sub Class", but instead it outputs
> > >"Super class".
>
> > >It would sem that static functions can't work with overridden
> > >constants in subclasses, or am I missing something?
>
> > Currently static references are resolved at compile time. What you need
> > here is called late static binding and scheduled for PHP 5.3.
>
> > Micha
>
> Thanks.
>
> Is there any kind of a workaround possible in older versions? =A0The
> only way I've found to get it to work as intended is to "inherit from
> the clipboard" and cut and paste the methods into all the classes.
> Maintainence nightmare.

Theoratically speaking, a constant that needs to change during
execution is not a constant.
Could you explain the context a bit more ? I don't really see what
you're trying to do in your "simple" example.

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