Hướng dẫn php date_default_timezone_set not working

date_default_timezone_set not working.

my code:

ini_set('display_errors', true);
error_reporting(E_ALL);

date_default_timezone_set("UTC");
echo date('Y-m-d H:i:s T') . "
";
echo date('Y-m-d H:i:s T', time()) . "
";
date_default_timezone_set("Asia/Shanghai");
echo date('Y-m-d H:i:s T') . "
";
echo date('Y-m-d H:i:s T', time()) . "
";
ini_set("date.timezone","UTC");
echo date('Y-m-d H:i:s T') . "
";
echo date('Y-m-d H:i:s T', time()) . "
";
ini_set("date.timezone","Asia/Shanghai");
echo date('Y-m-d H:i:s T') . "
";
echo date('Y-m-d H:i:s T', time()) . "
";

all of them return the same date "2017-05-26 12:47:08 CST", why?

update:

I have fixed this problem, the reason is that I used the wrong way to change the timezone on CentOS7:

cp /usr/share/zoneinfo/Asia/Shanghai /etc/localtime

this way is right on CentOS6, but in CentOS7 /etc/localtime is linked to /usr/share/zoneinfo/Etc/UTC, so I damaged the UTC timezone.

the right way to change the timezone on CentOS7 is:

timedatectl set-timezone "Asia/Shanghai"

or

ln -sf /usr/share/zoneinfo/Asia/Shanghai /etc/localtime

so I copied /usr/share/zoneinfo/Etc/UTC from other system to my system to fixed this problem.