PHP 7 array_values assignment

<?php
$ar = array('foo');
unset($ar[0]);
$ar = array_values($ar);
$ar[] = 'bar';
var_dump($ar);
/*
PHP 5:
array(1) {
  [0] =>
  string(3) "bar"
}
 
PHP 7:
array(1) {
  [1]=>
  string(3) "bar"
}
*/
?>