Index: user/selector/script.js
===================================================================
RCS file: user/selector/script.js
diff -N user/selector/script.js
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ user/selector/script.js	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,1 @@
+// JavaScript for the user selectors.
Index: user/selector/test.php
===================================================================
RCS file: user/selector/test.php
diff -N user/selector/test.php
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ user/selector/test.php	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,43 @@
+<?php
+require_once(dirname(__FILE__) . '/../../config.php');
+require_once($CFG->dirroot . '/user/selector/lib.php');
+
+class test_user_selector extends user_selector_base {
+    public function __construct($name) {
+        parent::__construct($name);
+    }
+
+    protected function find_users($search) {
+        list($wherecondition, $params) = $this->search_sql($search, 'u');
+        $sql = 'SELECT ' . $this->required_fields_sql('u') .
+                'FROM {user} u ' .
+                'WHERE ' . $wherecondition;
+        $users = get_recordset_sql($sql, $params);
+        $groupedusers = array();
+        foreach ($users as $user) {
+            $groupedusers['Users matching ' . s($search)][] = $user;
+        }
+        return $groupedusers;
+    }
+}
+
+print_header();
+
+$userselector = new test_user_selector('myuserselector');
+
+$users = $userselector->get_selected_users();
+if (!empty($users)) {
+    print_heading('Users that were selected');
+    echo '<ul>';
+    foreach ($users as $user) {
+        echo '<li>', fullname($user), '</li>';
+    }
+    echo '</ul>';
+}
+
+echo '<p><label for="myuserselector">Select users</label>';
+$userselector->display();
+echo '</p>';
+
+print_footer();
+?>
Index: user/selector/lib.php
===================================================================
RCS file: user/selector/lib.php
diff -N user/selector/lib.php
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ user/selector/lib.php	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,106 @@
+<?php  // $Id$
+
+///////////////////////////////////////////////////////////////////////////
+//                                                                       //
+// NOTICE OF COPYRIGHT                                                   //
+//                                                                       //
+// Moodle - Modular Object-Oriented Dynamic Learning Environment         //
+//          http://moodle.org                                            //
+//                                                                       //
+// Copyright (C) 1999 onwards Martin Dougiamas  http://dougiamas.com     //
+//                                                                       //
+// This program is free software; you can redistribute it and/or modify  //
+// it under the terms of the GNU General Public License as published by  //
+// the Free Software Foundation; either version 2 of the License, or     //
+// (at your option) any later version.                                   //
+//                                                                       //
+// This program is distributed in the hope that it will be useful,       //
+// but WITHOUT ANY WARRANTY; without even the implied warranty of        //
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         //
+// GNU General Public License for more details:                          //
+//                                                                       //
+//          http://www.gnu.org/copyleft/gpl.html                         //
+//                                                                       //
+///////////////////////////////////////////////////////////////////////////
+
+/**
+ * Code for ajax user selectors.
+ *
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package userselector
+ */
+
+abstract class user_selector_base {
+    protected $name;
+    protected $exclude = array();
+    protected $extrafields;
+
+    // This is used by get selected users, 
+    private $validatinguserids = null;
+
+    public function __construct($name) {
+        global $CFG;
+        $this->name = $name;
+        if (empty($CFG->extrauserselectorfields)) {
+            $this->extrafields = array();
+        } else {
+            $this->extrafields = explode(',', $CFG->extrauserselectorfields);
+        }
+    }
+
+    public function exclude($arrayofuserids) {
+        $exclude = array_unique(array_merge($exclude));
+    }
+
+    public function get_selected_users() {
+        $this->validatinguserids = optional_param($this->name, array(), PARAM_INTEGER);
+        $groupedusers = $this->find_users('');
+        $this->validatinguserids = null;
+        $users = array();
+        foreach ($groupedusers as $group) {
+            $users = array_merge($users, $group);
+        }
+        return $users;
+    }
+
+    public function display() {
+        // TODO
+    }
+
+    protected abstract function find_users($search);
+
+    protected function get_options() {
+        return array(
+            'class' => get_class($this),
+            'exclude' => $this->exclude,
+        );
+    }
+
+    protected function required_fields_sql($u) {
+        global $DB;
+        $DB = new moodle_database;
+        $fields = array(
+             $u . '.id',
+             $DB->sql_fullname($u . '.firstname', $u . '.lastname'),
+        );
+        foreach ($this->extrafields as $field) {
+            $fields[] = $u . '.' . $field;
+        }
+        return implode(',', $fields);
+    }
+
+    protected function search_sql($search, $u) {
+        $conditions = array(
+            
+        );
+    }
+}
+
+class role_assign_user_selector extends user_selector_base {
+    // TODO
+}
+
+class group_members_user_selector extends user_selector_base {
+    // TODO
+}
+?>
Index: user/selector/search.php
===================================================================
RCS file: user/selector/search.php
diff -N user/selector/search.php
--- /dev/null	1 Jan 1970 00:00:00 -0000
+++ user/selector/search.php	1 Jan 1970 00:00:00 -0000
@@ -0,0 +1,36 @@
+<?php  // $Id$
+
+///////////////////////////////////////////////////////////////////////////
+//                                                                       //
+// NOTICE OF COPYRIGHT                                                   //
+//                                                                       //
+// Moodle - Modular Object-Oriented Dynamic Learning Environment         //
+//          http://moodle.org                                            //
+//                                                                       //
+// Copyright (C) 1999 onwards Martin Dougiamas  http://dougiamas.com     //
+//                                                                       //
+// This program is free software; you can redistribute it and/or modify  //
+// it under the terms of the GNU General Public License as published by  //
+// the Free Software Foundation; either version 2 of the License, or     //
+// (at your option) any later version.                                   //
+//                                                                       //
+// This program is distributed in the hope that it will be useful,       //
+// but WITHOUT ANY WARRANTY; without even the implied warranty of        //
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         //
+// GNU General Public License for more details:                          //
+//                                                                       //
+//          http://www.gnu.org/copyleft/gpl.html                         //
+//                                                                       //
+///////////////////////////////////////////////////////////////////////////
+
+/**
+ * Code to search for users in response to an ajax call from a user selector.
+ *
+ * @license http://www.gnu.org/copyleft/gpl.html GNU Public License
+ * @package userselector
+ */
+
+require_once(dirname(__FILE__) . '/../../config.php');
+require_once($CFG->dirroot . '/user/selector/lib.php');
+
+?>