[PHP] Timezone management

[Lamonte H]

After a while of studying different softwares,  I've still been getting
confused on how to make a timezone management script to display time in
different time zones.  Like right now im in -0600 CST GMT,  how would I
create a script that would work on any server that would allow me to display
my current time from -12 to 12 GMT in a select box so others could pick
their own time also.