class  TestClass { }

$TestObj=new TestClass();

$TestObj_assigned=$TestObj;
$TestObj_Refrenced=&$TestObj;
$TestObj_cloned=clone $TestObj;

$obj=new ReflectionClass('TestClass');

var_dump($obj->isInstance($TestObj)); 
var_dump($obj->isInstance($TestObj_assigned)); 
var_dump($obj->isInstance($TestObj_Refrenced)); 
var_dump($obj->isInstance($TestObj_cloned));