The gettext functions implement an NLS (Native Language Support) API which can be used to internationalize your PHP applications. Please see the gettext documentation for your system for a thorough explanation of these functions or view the docs at http://www.gnu.org/software/gettext/manual/index.html.
To use these functions you must download and install the GNU gettext package from http://www.gnu.org/software/gettext/gettext.html
To include GNU gettext support in your PHP build you must add the option --with-gettext[=DIR] where DIR is the gettext install directory, defaults to /usr/local.
Note to Win32 Users: In order to enable this module on a Windows environment, you must copy gnu_gettext.dll from the DLL folder of the PHP/Win32 binary package to the SYSTEM32 folder of your windows machine. (Ex: C:\WINNT\SYSTEM32 or C:\WINDOWS\SYSTEM32). Starting with PHP 4.2.3 the name changed to libintl-1.dll, this requires also iconv.dll to be copied.