Create a date from week number and day number

Hi experts!

Recently I have been asked to write a function that can create a date from a week number and day number for the 2 previous years.

I can't quite figure it out, i've looked everywhere on the net but no go.

This is what i have so far;

<?php>
//Get the week number and day number
//Current Week Number
$tw=date("W");

//Current Day Number
$td=date("w");

//This Year
$y=date("Y");
//Last year
$ly=$y-1;
//2 Years Ago
$l2y=$y-2;

//Need the day in format yyyy-mm-dd
//Not sure what to do
<?php>

Any help would be greatly appreciated, as I'm pulling out my hair. I've worked with dates and times before in php, but this has me stumped.

Thanks in advanceStart Free Trial