PHP学习：php实现求相对时间函数

<?php
function relativeTime($time = false, $limit = 86400, $format = 'g:i A M jS') {
  if (empty($time) || (!is_string($time) & amp; & amp;
  !is_numeric($time))) $time = time();
  elseif (is_string($time)) $time = strtotime($time);
  $now = time();
  $relative = '';
  if ($time === $now) $relative = 'now';
  elseif ($time > $now) $relative = 'in the future';
  else {
    $diff = $now - $time;
    if ($diff >= $limit) $relative = date($format, $time);
    elseif ($diff < 60) {
      $relative = 'less than one minute ago';
    } elseif (($minutes = ceil($diff / 60)) < 60) {
      $relative = $minutes . ' minute' . (((int)$minutes === 1) ? '' : 's') . ' ago';
    } else {
      $hours = ceil($diff / 3600);
      $relative = 'about ' . $hours . ' hour' . (((int)$hours === 1) ? '' : 's') . ' ago';
    }
  }
  return $relative;
}