继承静态方法

Question

I have the following problem; there are 2 models in my application, but they are stored in the same table in my database. They can be differentiated by their type column, the first being 0 and the second 1.

In my application i've made 2 classes, one for each type. However i'd only want to create the queries once, and use a static member to figure out the type. Basicly what i want to achieve would look like this:

class A
{
    public $Description; //From the database

    public static function GetAll()
    {
        $query = "SELECT * FROM letters WHERE type = " . self::getType();

        echo $query;
    }

    private static function getType()
    {
        return 0;
    }
}

class B
    extends A
{
    public $SomeOtherProperty; //B also has another property, which A doesnt have. Its stored an another table.

    private static function getType()
    {
        return 1;
    }
}

A::GetAll(10);
B::GetAll(10);

However, PHP doesnt support static memberwriting, which results in this output:

SELECT * FROM letters WHERE type = 0

SELECT * FROM letters WHERE type = 0

What's the best way to achieve such a result, where the child-class can specify its own type?

Answer 1

First of all, you should use protected visibility when you inherit the method getType():

protected static function getType();

And for getting current type, use PHP 5.3 new feature of static keyword: http://php.net/manual/en/language.oop5.late-static-bindings.php

$query = "SELECT * FROM letters WHERE type = " . static::getType();

Static ensures the late binding will be used so the method of actual type will be used.