php - PHP grabbing Year and Month

Question

   $str = $in_Date;
   echo " " . $str;
while(! feof($str)){
   $letter = parse_str($str);
   echo " " . $letter;
}
    $date = array("$letter");
    echo " " . $date[0];
    echo " " . $date[1];

So for example $in_Date=20131016 so YYYYMMDD

What I want to do is but each character in an array so then I can grab 0-3 which would be the year then grab the month 3-4..

it works all the way to the line before the while statement... So i think my while statement is wrong