php date format YYYY-MM-DD minus or add one week from now?

Question

today 22-05-2011 so it should be 29-05-2011? ( plus 1 week ) 
or
today 22-05-2011 so it should be 15-05-2011? ( minus 1 week ) 

thanks for looking

Answer 1

Use strtotime()

echo date('d-m-Y', strtotime("+1 week")); //1 week in the future
echo date('d-m-Y', strtotime("-1 week")); //1 week ago