(PHP 4, PHP 5)
setlocale — Set locale information
$category
   , string $locale
   [, string $...
  ] )$category
   , array $locale
   )Sets locale information.
category
       category is a named constant specifying the
       category of the functions affected by the locale setting:
       
LC_ALL for all of the below
         
        LC_COLLATE for string comparison, see
          strcoll()
         
        LC_CTYPE for character classification and conversion, for
          example strtoupper()
         
        LC_MONETARY for localeconv()
         
        LC_NUMERIC for decimal separator (See also
          localeconv())
         
        LC_TIME for date and time formatting with
          strftime()
         
        LC_MESSAGES for system responses (available if PHP was compiled with
          libintl)
         
        locale
       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.
      
...(Optional string or array parameters to try as locale settings until success.)
Note:
On Windows, setlocale(LC_ALL, '') sets the locale names from the system's regional/language settings (accessible via Control Panel).
   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.
Note:
The return value of setlocale() depends on the system that PHP is running. It returns exactly what the system setlocale function returns.
| Version | Description | 
|---|---|
| 7.0.0 | Support for the categoryparameter passed as a string has
        been removed. Only LC_* constants can be used as of this version. | 
| 5.3.0 | This function now throws an E_DEPRECATEDnotice if a string is passed 
        to thecategoryparameter instead of one of the 
        LC_* constants. | 
Example #1 setlocale() Examples
<?php
/* Set locale to Dutch */
setlocale(LC_ALL, 'nl_NL');
/* Output: vrijdag 22 december 1978 */
echo strftime("%A %e %B %Y", mktime(0, 0, 0, 12, 22, 1978));
/* try different possible locale names for german as of PHP 4.3.0 */
$loc_de = setlocale(LC_ALL, 'de_DE@euro', 'de_DE', 'de', 'ge');
echo "Preferred locale for german on this system is '$loc_de'";
?>
Example #2 setlocale() Examples for Windows
<?php
/* Set locale to Dutch */
setlocale(LC_ALL, 'nld_nld');
/* Output: vrijdag 22 december 1978 */
echo strftime("%A %d %B %Y", mktime(0, 0, 0, 12, 22, 1978));
/* try different possible locale names for german as of PHP 4.3.0 */
$loc_de = setlocale(LC_ALL, 'de_DE@euro', 'de_DE', 'deu_deu');
echo "Preferred locale for german on this system is '$loc_de'";
?>
The locale information is maintained per process, not per thread. If you are running PHP on a multithreaded server API like IIS, HHVM or Apache on Windows, you may experience sudden changes in locale settings while a script is running, though the script itself never called setlocale(). This happens due to other scripts running in different threads of the same process at the same time, changing the process-wide locale using setlocale().
    Windows users will find useful information about
    locale strings at Microsoft's
    MSDN website. Supported language strings can be found
    in the
    » language strings documentation
    and supported country/region strings in the
    » country/region strings documentation.