Early and Late static binding in PHP. Code example

class Transport{
  public static $model = 'transport';
  public static function getModel() {
    return self::$model;
  }
}

class Car extends Transport{
  public static $model = 'car';
}

echo Car::getModel(); // 'transport'

return self::$model – points to the current class, so the result is ‘transport’, this mechanism is also called “Early static binding“.

class Transport{
  public static $model = 'transport';
  public static function getModel() {
    return static::$model;
  }
}

class Car extends Transport{
  public static $model = 'car';
}

echo Car::getModel(); // 'car'

If the word “self” is replaced by “static“, then we get “late static binding“, i.e. the connection will be established with the class that calls this code, as a result we get the value “car”.