instanceof php

<?php
class A{}
class B{}
class ncccc extends B{}

$a = new A();
$b = new B();
$vvv = new ncccc();
$test1 = ($a instanceof  A);
$test = ($vvv instanceof  b);
if( $test1 ){
echo " is class A object";
}
else{
echo " not is class A object";
}
echo "<br>";
if( $test ){
echo " is ok ";
}
else{
echo " shibai ";
}