参考：https://www.cnblogs.com/water0729/p/5803217.html

<?php

class foo {
    static public function test() {
        echo "foo.__CLASS__：".__CLASS__."\n";
        echo "foo.get_class：".get_class()."\n";
        echo "foo.get_called_class：".get_called_class()."\n";
    }
}

class bar extends foo {
    
}

foo::test();
echo "\n";
bar::test();
?>
//结果
foo.__CLASS__：foo
foo.get_class：foo
foo.get_called_class：foo

foo.__CLASS__：foo
foo.get_class：foo
foo.get_called_class：bar

1.__CLASS__：获取当前的类名

2.get_class()：返回对象的类名

3.get_called_class()：后期静态绑定（"Late Static Binding"）类的名称，即静态方法调用者的类名

<?php

//通过get_called_class实现单例模式

class Singleton{
   
　  private static $instance; 
　　
    public static function getInstance() {
        $class_name = get_called_class();
        if (isset(self::$instance[$class_name])) {
            return self::$instance[$class_name];
        }
        self::$instance[$class_name] = new $class_name;
        return self::$instance[$class_name];
    }
}

?>