设置时区

方法1：
（最好的方法）在php.ini里加上找到date.timezone项，设置date.timezone = "Asia/Shanghai"，重启环境就ok了。

方法2：
在需要用到这些时间函数的时候，在页面添加date_default_timezone_set("PRC");

方法3：
在页头加上设置时区ini_set('date.timezone','Asia/Shanghai');

错误代码：
Warning: date(): It is not safe to rely on the system’s timezone settings. You are *required* to use the date.timezone setting 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 ‘Asia/Chongqing’ for ‘CST/8.0/no DST’ instead