Tak patrzę i patrzę i to powinno działać :
/**
* Central setlocale method so we can adjust as needed
*
* @access public
* @param string Locale to set
* @return void
* @link http://community.invisionpower.com/tracker/issue-16386-language-locale-gives-error/
* @link http://community.invisionpower.com/tracker/issue-18424-change-lang-locale/
*/
static public function setlocale( $locale='' )
{
if( !$locale )
{
return;
}
if ( stripos( $locale, 'tr_' ) !== FALSE )
{
setlocale( LC_COLLATE, $locale );
setlocale( LC_MONETARY, $locale );
setlocale( LC_NUMERIC, $locale );
setlocale( LC_TIME, $locale );
setlocale( LC_MESSAGES, $locale );
}
else
{
setlocale( LC_ALL, $locale );
}
}