title: Get the first week day in a given week number in PHP
body: <p>How can I get the first week day in a given week number?
  I'm making a function in PHP for a calendar app.</p>
  
  <p>The idea: When I click on a link that basically uses strtotime with +1 month it only jumps to that same day of course. I need to get the week numbers correct.</p>
  
  <p>Example: When I use the menu to move from August to September, it shouldn't select the same date I was in in August, but the first day of the first week number in September (Monday, 2th of September, week number 36).</p>
  
  <p>And from September to October: Week number 40, Tuesday the 1th of October.</p>