Tratamento de diversos formato de data em PHP

date_grab.php

<?php
function date_grab($str)
{
  // regex pattern will match any date formatted dd-mm-yyy or d-m-y with
  // separators: periods, slahes, dashes
  $p = '{.*?(\d\d?)[\\/\.\-]([\d]{2})[\\/\.\-]([\d]{4}).*}';
  $date = preg_replace($p, '$3-$2-$1', $str);
  return new \DateTime($date, new DateTimeZone('America/Sao_Paulo'));
}


$arr = array(
    "03/12/2011 (Sat)",
    "3.12.2011 SAT",
    "Date: 03/12/2011 ", /* <-- the extra trailing space is intentional */
    "date:03/12/2011",
    "date: 03/12/2011",
    "03/12/2011",
    "10/10/11"
);
foreach ($arr as $str) {
    $date = date_grab($str);
    echo $date->format('Y-m-d') . "\n";
}