LC_TIME for date and time formatting with
LC_MESSAGES for system responses (available if PHP was compiled with
As of PHP 4.2.0, passing category as a string is
deprecated, use the above constants instead. Passing them as a string
(within quotes) will result in a warning message.
If locale is NULL or the empty string
"", the locale names will be set from the
values of environment variables with the same names as the above
categories, or from "LANG".
If locale is "0",
the locale setting is not affected, only the current setting is returned.
If locale is an array or followed by additional
parameters then each array element or parameter is tried to be set as
new locale until success. This is useful if a locale is known under
different names on different systems or for providing a fallback
for a possibly not available locale.
Passing multiple locales is not available before PHP 4.3.0
Setlocale returns the new current locale, or FALSE if the locale
functionality is not implemented on your platform, the specified
locale does not exist or the category name is invalid.
An invalid category name also causes a warning message. Category/locale
names can be found in RFC 1766
and ISO 639.
Different systems have different naming schemes for locales.
The return value of setlocale() depends
on the system that PHP is running. It returns exactly
what the system setlocale function returns.
The locale information is maintained per process, not per
thread. If you are running PHP on a multithreaded server
api like IIS or Apache on Windows you may experience
sudden changes of locale settings while a script is
running although the script itself never called setlocale()
itself. This happens due to other scripts running in different
threads of the same process at the same time changing the
processwide locale using setlocale().