Modificare una stringa data php

[k.b]

<?php
$data_ita = preg_replace("/(\\d\\d)(\\d\\d)(\\d\\d\\d\\d)/", "$1/$2/$3", $data_ita);
$data_ame = preg_replace("/(\\d\\d\\d\\d)(\\d\\d)(\\d\\d)/", "$3/$2/$1", $data_ame);
?>