Calculate the interval between two dates, then format the interval in PHP

/*from   w w  w  .  j  a v  a 2s . co m*/
<?php
    $date1=date_create("2013-01-01");
    $date2=date_create("2013-02-10");
    $diff=date_diff($date1,$date2);

    // %a outputs the total number of days
    echo $diff->format("Total number of days: %a.");

/*
      % - Literal %
      Y - Year, at least 2 digits with leading zero (e.g 03)
      y - Year (e.g 3)
      M - Month, with leading zero (e.g 06)
      m - Month (e.g 6)
      D - Day, with leading zero (e.g 09)
      d - Day (e.g 9)
      a - Total number of days as a result of date_diff()
      H - Hours, with leading zero (e.g 08, 23)
      h - Hours (e.g 8, 23)
      I - Minutes, with leading zero (e.g 08, 23)
      i - Minutes (e.g 8, 23)
      S - Seconds, with leading zero (e.g 08, 23)
      s - Seconds (e.g 8, 23)
      R - Sign "-" when negative, "+" when positive
      r - Sign "-" when negative, empty when positive

      Each format character must be prefixed by a % sign!
*/
?>