+
+ /**
+ * Returns the raw sort key to be used for categories, with the specified
+ * prefix. This will be fed to Language::convertToSortkey() to get a
+ * binary sortkey that can be used for actual sorting.
+ *
+ * @param $prefix string The prefix to be used, specified using
+ * {{defaultsort:}} or like [[Category:Foo|prefix]]. Empty for no
+ * prefix.
+ * @return string
+ */
+ public function getCategorySortkey( $prefix = '' ) {
+ $unprefixed = $this->getText();
+ if ( $prefix !== '' ) {
+ # Separate with a null byte, so the unprefixed part is only used as
+ # a tiebreaker when two pages have the exact same prefix -- null
+ # sorts before everything else (hopefully).
+ return "$prefix\0$unprefixed";
+ }
+ return $unprefixed;
+ }