<?php
function timeDifference($oldtime) {
  $time = time(); // Get the unix timestamp for today
  $elapsed = $time - $oldtime; // How many seconds between today and the date in question
  $years = date('Y', $elapsed) - 1970; // Calculate the year subtracting the beginning year 1970
  $months = date('n', $elapsed); // Calculate months
  $days = date('j', $elapsed); // Calculate days
  return array('years'=>$years, 'months'=>$months, 'days'=>$days); // Return values as an array
}
?>

<?php
$difference = timeDifference(mktime(0, 0, 0, 9, 23, 1986)); // Specify unix timestamp in timeDifference()
echo 'Time elapsed: '.$difference['years'].' years, '.$difference['months'].' months, '.$difference['days'].' days'; // Echo each variable in $difference
?>