php mktime()函数错误，高手帮帮忙，在线等回复

php版本6.0

<?php
       echo "mktime函数返回的时间戳：".mktime()."<p>";
?>
mktime()的参数直接是空会错误吗？应该是可以省略的吧？
错误提示
Strict Standards: mktime() [function.mktime]: It is not safe to rely on the system's timezone settings. Please use the date.timezone setting, the TZ environment variable or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected 'UTC' for '8.0/no DST' instead in F:\AppServ\www\phpweb\10\6\index.php on line 23

Strict Standards: mktime() [function.mktime]: You should be using the time() function instead in F:\AppServ\www\phpweb\10\6\index.php on line 23
mktime函数返回的时间戳：1314760412

[ 本帖最后由 sunles 于 2011-8-31 12:57 编辑 ]

http://aiyooyoo.com/index.php/archives/444/

time()和mktime()的区别，查手册即可，很简单的问题。

我想知道mktime()函数里面的参数不能省略吗？
我看手册手参数可以省略的，省略的参数被设置成本地日期和时间的当前值？