money_format gives error

[nebulom]

Having a code like

<?php

    $a = 1232322210.44;

    setlocale (LC_MONETARY, 'en_US');

    echo money_format ("%n", $a);
    echo "\n";
    echo money_format ("%i", $a);
    echo "\n";

?>

gives an error like Fatal error: Call to undefined function money_format() in C:\Program Files\Apache Group\Apache2\htdocs\test\test.php on line 7. Am I missing something?