title: Add 7 days to datetime (rather than just date) in php
body: <p>I'm currently getting a datetime from a form that is stored in mysql like this:</p>
  
  <pre><code>2013-03-18 09:00:00
  </code></pre>
  
  <p>However for the function I am building, I'm inserting an event into a calendar where each week is less than the final week, essentially the insert is replicated except that the start date has changed.</p>
  
  <p>So I get the post like this:</p>
  
  <pre><code>if (isset($_POST['submit']))
  {
      echo $start = $_POST['startDT'].':00';
  }
  </code></pre>
  
  <p>This works. So does the function for putting it in for one week only. What I'm stuck on, is replicating it across weeks.</p>
  
  <p>So my function looks like this:</p>
  
  <pre><code>if ($allYear = "yes")
  {
      //Get Week in question - gives me the week number for that particular week
      $startW = getStartWeek($start);
          //It'll always be week 56 as the end week of the year
      $endW = 56;
          //while $i is less than or equal to 56, do it and add 1 to $i
      for($i = $startW; $i &lt;= $endw; $i++)
      {
          $query = $mysqli-&gt;prepare("INSERT INTO `Events`(`Start`, `End`, `Group`, `Unit`, `Type`, `Room`, `Lecturer`) VALUES ('$start', '$end', '$group', '$unit', '$type', '$room', '$lecturer')");
          /*Here is where I'd add code to make the datetime, for example:
          * $start is 2013-03-18 09:00:00 and $end is 2013-03-18 10:00:00
          * I want $start in the next iteration to be 2013-03-25 09:00:00 and $end
          * to be 2013-03-25 10:00:00. I then want $start to be 2013-04-01 09:00:00
          * on the iteration after that. And so on.
          */
          $start += strtotime("+1 week");
          $end += strtotime("+1 week");
      }
  }
  </code></pre>