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

The need for abstract properties can indicate design problems. While many of answers implement kind of Template method pattern and it works, it always looks kind of strange.

Let's take a look at the original example:

abstract class Foo_Abstract {
    abstract public $tablename;
}

class Foo extends Foo_Abstract {
    //Foo must 'implement' $property
    public $tablename = 'users';   
}

To mark something abstract is to indicate it a must-have thing. Well, a must-have value (in this case) is a required dependency, so it should be passed to the constructor during instantiation:

class Table
{
    private $name;

    public function __construct(string $name)
    {
        $this->name = $name;
    }

    public function name(): string
    {
        return $this->name;
    }
}

Then if you actually want a more concrete named class you can inherit like so:

final class UsersTable extends Table
{
    public function __construct()
    {
        parent::__construct('users');
    }
}

This can be useful if you use DI container and have to pass different tables for different objects.