<?php
$array 
= [012];
$ref1 =& $array[1];
$ref2 =& $array[2];
$array[3] =& $array[2];

$r0 ReflectionReference::fromArrayElement($array0);
$r1 ReflectionReference::fromArrayElement($array1);
$r2 ReflectionReference::fromArrayElement($array2);
$r3 ReflectionReference::fromArrayElement($array3);

var_dump$r0$r1 );

echo 
base64_encode$r1->getId() ), "\n";
echo 
base64_encode$r2->getId() ), "\n";
echo 
base64_encode$r3->getId() ), "\n";
Output
NULL object(ReflectionReference)#499 (0) { } zZC9I8IOqYVXFwtvBK+H0Lu+k70= LKzX6/HtqU1Xvx8SJJEh14uT8Sk= LKzX6/HtqU1Xvx8SJJEh14uT8Sk=