Late Static Binding

1.php

<?php

abstract class Car
{
    protected static $price;
    public static function getFormattedPrice()
    {
        return number_format(self::$price);
    }
}

class NissanNote extends Car
{
    protected static $price = 1400000;
}

echo NissanNote::getFormattedPrice();
// 0

2.php

<?php

abstract class Car
{
    protected static $price;
    public static function getFormattedPrice()
    {
        return number_format(static::$price);
    }
}

class NissanNote extends Car
{
    protected static $price = 1400000;
}

echo NissanNote::getFormattedPrice();
// 1,400,000

3.php

<?php

abstract class Car
{
    protected static $price;

    public static function getFormattedPrice()
    {
        return number_format(static::$price);
    }

    public static function getDescription()
    {
        return 'price is ' . Car::getFormattedPrice(); // 非転送コール
    }
}

class NissanNote extends Car
{
    protected static $price = 1400000;
}

echo NissanNote::getDescription();
// price is 0