PHP How to reverse engineer the day of the year 3212 (YDDD) into 2013-08-01 (YYYY-mm-dd)

Question

I have a date in YDDD format such 3212
I want to convert this date into default date string i.e. 2013-08-01 in PHP
Since the first value Y is the only character for Year, so I've decided to take the first three characters from the current Year i.e. 201 from 2013
The following is the code I've written for year

<?php
$date = "3212"
$y = substr($date,0,1); // will take out 3 out of year 3212
$ddd = substr($date,1,3); // will take out 212 out of year 3212
$year = substr(date("Y"),0,3) . $y; //well create year "2013"
?>

Now How can I use $year and 212 to convert it into 2013-08-01 using PHP

EDIT
FYI: My PHP Version is 5.3.6

Answer 1

$date = "3212";
echo DateTime::createFromFormat("Yz", "201$date")->format("Y-m-d");
// 2013-08-01

• DateTime::createFromFormat()
• See it running online