Abstract constants in PHP - Force a child class to define a constant

Question

I noticed that you can\'t have abstract constants in PHP.

Is there a way I can force a child class to define a constant (which I need to use in one of the abstract c

Answer 1

No, yet you could try other ways such as abstract methods:

abstract class Fruit
{
    abstract function getName();
    abstract function getColor();

    public function printInfo()
    {
        echo "The {$this->getName()} is {$this->getColor()}";
    }
}

class Apple extends Fruit
{
    function getName() { return 'apple'; }
    function getColor() { return 'red'; }

    //other apple methods
}

class Banana extends Fruit
{
    function getName() { return 'banana'; }
    function getColor() { return 'yellow'; }

    //other banana methods
}  

or static members:

abstract class Fruit
{
    protected static $name;
    protected static $color;

    public function printInfo()
    {
        echo "The {static::$name} is {static::$color}";
    }
}

class Apple extends Fruit
{
    protected static $name = 'apple';
    protected static $color = 'red';

    //other apple methods
}

class Banana extends Fruit
{
    protected static $name = 'banana';
    protected static $color = 'yellow';

    //other banana methods
} 

Source