self和static的差异

其实很简单。

在没有继承的情况下是一样的。主要的差异体现在继承的情况下。

差异：

self：永远绑定代码所在类。当前定义类
static：调用时确定哪个类。当前调用类

class Books
{
    public static $title = 'Books';
    public static function getTitleSelf()
    {
        return self::$title;
    }
    public static function getTitleStatic()
    {
        return static::$title;
    }
}
class SmallBook extends Books
{
    public static $title = 'small';
}

echo SmallBook::getTitleSelf().'<br />';
echo SmallBook::getTitleStatic().'<br />';
echo Books::getTitleStatic().'';
echo Books::getTitleSelf().'';

运行结果：

Books
small
Books
Books