-if (! function_exists('tt')){
-function tt($singular, $plural, $count){
+/**
+ * @brief Return the localized version of a singular/plural string with optional string interpolation
+ *
+ * This function takes two english strings as parameters, singular and plural, as
+ * well as a count. If a localized version exists for the current language, they
+ * are used instead. Discrimination between singular and plural is done using the
+ * localized function if any or the default one. Finally, a string interpolation
+ * is performed using the count as parameter.
+ *
+ * Usages:
+ * - tt('Like', 'Likes', $count)
+ * - tt("%s user deleted", "%s users deleted", count($users))
+ *
+ * @global type $lang
+ * @param string $singular
+ * @param string $plural
+ * @param int $count
+ * @return string
+ */
+function tt($singular, $plural, $count)
+{