PHP abstract properties

Question

Is there any way to define abstract class properties in PHP?

abstract class Foo_Abstract {
    abstract public $tablename;
}

class Foo extends Foo_Abstract          


        

Answer 1

Depending on the context of the property if I want to force declaration of an abstract object property in a child object, I like to use a constant with the static keyword for the property in the abstract object constructor or setter/getter methods. You can optionally use final to prevent the method from being overridden in extended classes.

Other than that the child object overrides the parent object property and methods if redefined. For example if a property is declared as protected in the parent and redefined as public in the child, the resulting property is public. However if the property is declared private in the parent it will remain private and not available to the child.

http://www.php.net//manual/en/language.oop5.static.php

abstract class AbstractFoo
{
    public $bar;

    final public function __construct()
    {
       $this->bar = static::BAR;
    }
}

class Foo extends AbstractFoo
{
    //const BAR = 'foobar';
}

$foo = new Foo; //Fatal Error: Undefined class constant 'BAR' (uncomment const BAR = 'foobar';)
echo $foo->bar;