title: Round Datetime to the next 15 minutes
body: <p>in my project I need to round a date time e.g "08:10" to "08:00".</p>
  
  <p>more examples</p>
  
  <p>"8:20 to 8:15"
  "8:31 to 8:30"</p>
  
  <p>And in the next step i need an extra method to round up.</p>
  
  <p>example
  "8:20 to 8:30"
  "8:31 to 8:45"</p>
  
  <pre class="lang-php prettyprint-override"><code>$shiftInPre = new \DateTime($row["time_start"] /* &lt;-e.g. 8:02*/);
  echo roundtoLastQuarterHour($shiftInPre);
  </code></pre>