Custom of converting American time to Beijing time in PHP

My server Beijing time, PHP call time: Date.timezone = "America/chicago"  This is a time in the United States side, sometimes with Beijing 13 hours, sometimes with Beijing time difference of 14 hours, so very difficult to deal with,
Now the PHP function can be processed, the following code, regardless of your time zone can be converted into our Beijing time:

Date ("Y-m-d h:i:s", Mktime (gmdate (' H ') +8,gmdate (' I '), gmdate (' s '), Gmdate (' m '), Gmdate (' d '), Gmdate (' Y ')));

Custom of converting American time to Beijing time in PHP