add phpDoc comment

git-svn-id: http://xe-core.googlecode.com/svn/branches/1.5.0@10780 201d5d3c-b55e-5fd7-737f-ddc643e51545

classes/xml/xmlquery/queryargument/SortQueryArgument.class.php

@@ -1,6 +1,15 @@
 <?php
-
+	/**
+	 * SortQueryArgument class
+	 * @author NHN (developers@xpressengine.com)
+	 * @package /classes/xml/xmlquery/queryargument
+	 * @version 0.1
+	 */
 	class SortQueryArgument extends QueryArgument{
+			/**
+			 * Change SortQueryArgument object to string
+			 * @return string
+			 */
             function toString(){
                 $arg = sprintf("\n" . '${\'%s_argument\'} = new SortArgument(\'%s\', %s);' . "\n"
                                         , $this->argument_name