diff --git a/phpBB/common.php b/phpBB/common.php
index 0ac7cbbd86..3586031c36 100644
--- a/phpBB/common.php
+++ b/phpBB/common.php
@@ -239,3 +239,9 @@ foreach ($cache->obtain_hooks() as $hook)
 {
 	@include($phpbb_root_path . 'includes/hooks/' . $hook . '.' . $phpEx);
 }
+
+if (!$config['use_system_cron'])
+{
+	require($phpbb_root_path . 'includes/cron.' . $phpEx);
+	$cron = new cron();
+}
diff --git a/phpBB/cron.php b/phpBB/cron.php
index 4462f52e93..1dbe1768c1 100644
--- a/phpBB/cron.php
+++ b/phpBB/cron.php
@@ -15,271 +15,58 @@ define('IN_CRON', true);
 $phpbb_root_path = (defined('PHPBB_ROOT_PATH')) ? PHPBB_ROOT_PATH : './';
 $phpEx = substr(strrchr(__FILE__, '.'), 1);
 include($phpbb_root_path . 'common.' . $phpEx);
+include($phpbb_root_path . 'includes/cron_lock.' . $phpEx);
 
 // Do not update users last page entry
 $user->session_begin(false);
 $auth->acl($user->data);
 
-$cron_type = request_var('cron_type', '');
-$use_shutdown_function = (@function_exists('register_shutdown_function')) ? true : false;
+function output_image() {
+	// Output transparent gif
+	header('Cache-Control: no-cache');
+	header('Content-type: image/gif');
+	header('Content-length: 43');
 
-// Output transparent gif
-header('Cache-Control: no-cache');
-header('Content-type: image/gif');
-header('Content-length: 43');
+	echo base64_decode('R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==');
 
-echo base64_decode('R0lGODlhAQABAIAAAP///wAAACH5BAEAAAAALAAAAAABAAEAAAICRAEAOw==');
-
-// test without flush ;)
-// flush();
-
-//
-if (!isset($config['cron_lock']))
-{
-	set_config('cron_lock', '0', true);
+	// test without flush ;)
+	// flush();
 }
 
-// make sure cron doesn't run multiple times in parallel
-if ($config['cron_lock'])
-{
-	// if the other process is running more than an hour already we have to assume it
-	// aborted without cleaning the lock
-	$time = explode(' ', $config['cron_lock']);
-	$time = $time[0];
-
-	if ($time + 3600 >= time())
-	{
-		exit;
+function do_cron($run_tasks) {
+	global $cron_lock;
+	
+	foreach ($run_tasks as $cron_type) {
+		$cron->run_task($cron_type);
 	}
-}
-
-define('CRON_ID', time() . ' ' . unique_id());
-
-$sql = 'UPDATE ' . CONFIG_TABLE . "
-	SET config_value = '" . $db->sql_escape(CRON_ID) . "'
-	WHERE config_name = 'cron_lock' AND config_value = '" . $db->sql_escape($config['cron_lock']) . "'";
-$db->sql_query($sql);
-
-// another cron process altered the table between script start and UPDATE query so exit
-if ($db->sql_affectedrows() != 1)
-{
-	exit;
-}
-
-/**
-* Run cron-like action
-* Real cron-based layer will be introduced in 3.2
-*/
-switch ($cron_type)
-{
-	case 'queue':
-
-		if (time() - $config['queue_interval'] <= $config['last_queue_run'] || !file_exists($phpbb_root_path . 'cache/queue.' . $phpEx))
-		{
-			break;
-		}
-
-		// A user reported using the mail() function while using shutdown does not work. We do not want to risk that.
-		if ($use_shutdown_function && !$config['smtp_delivery'])
-		{
-			$use_shutdown_function = false;
-		}
-
-		include_once($phpbb_root_path . 'includes/functions_messenger.' . $phpEx);
-		$queue = new queue();
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function(array(&$queue, 'process'));
-		}
-		else
-		{
-			$queue->process();
-		}
-
-	break;
-
-	case 'tidy_cache':
-
-		if (time() - $config['cache_gc'] <= $config['cache_last_gc'] || !method_exists($cache, 'tidy'))
-		{
-			break;
-		}
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function(array(&$cache, 'tidy'));
-		}
-		else
-		{
-			$cache->tidy();
-		}
-
-	break;
-
-	case 'tidy_search':
-		
-		// Select the search method
-		$search_type = basename($config['search_type']);
-
-		if (time() - $config['search_gc'] <= $config['search_last_gc'] || !file_exists($phpbb_root_path . 'includes/search/' . $search_type . '.' . $phpEx))
-		{
-			break;
-		}
-
-		include_once("{$phpbb_root_path}includes/search/$search_type.$phpEx");
-
-		// We do some additional checks in the module to ensure it can actually be utilised
-		$error = false;
-		$search = new $search_type($error);
-
-		if ($error)
-		{
-			break;
-		}
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function(array(&$search, 'tidy'));
-		}
-		else
-		{
-			$search->tidy();
-		}
-
-	break;
-
-	case 'tidy_warnings':
-
-		if (time() - $config['warnings_gc'] <= $config['warnings_last_gc'])
-		{
-			break;
-		}
-
-		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function('tidy_warnings');
-		}
-		else
-		{
-			tidy_warnings();
-		}
-
-	break;
-
-	case 'tidy_database':
-
-		if (time() - $config['database_gc'] <= $config['database_last_gc'])
-		{
-			break;
-		}
-
-		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function('tidy_database');
-		}
-		else
-		{
-			tidy_database();
-		}
-
-	break;
-
-	case 'tidy_sessions':
-
-		if (time() - $config['session_gc'] <= $config['session_last_gc'])
-		{
-			break;
-		}
-
-		if ($use_shutdown_function)
-		{
-			register_shutdown_function(array(&$user, 'session_gc'));
-		}
-		else
-		{
-			$user->session_gc();
-		}
-
-	break;
-
-	case 'prune_forum':
-
-		$forum_id = request_var('f', 0);
-
-		$sql = 'SELECT forum_id, prune_next, enable_prune, prune_days, prune_viewed, forum_flags, prune_freq
-			FROM ' . FORUMS_TABLE . "
-			WHERE forum_id = $forum_id";
-		$result = $db->sql_query($sql);
-		$row = $db->sql_fetchrow($result);
-		$db->sql_freeresult($result);
-
-		if (!$row)
-		{
-			break;
-		}
-
-		// Do the forum Prune thang
-		if ($row['prune_next'] < time() && $row['enable_prune'])
-		{
-			include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
-
-			if ($row['prune_days'])
-			{
-				if ($use_shutdown_function)
-				{
-					register_shutdown_function('auto_prune', $row['forum_id'], 'posted', $row['forum_flags'], $row['prune_days'], $row['prune_freq']);
-				}
-				else
-				{
-					auto_prune($row['forum_id'], 'posted', $row['forum_flags'], $row['prune_days'], $row['prune_freq']);
-				}
-			}
-
-			if ($row['prune_viewed'])
-			{
-				if ($use_shutdown_function)
-				{
-					register_shutdown_function('auto_prune', $row['forum_id'], 'viewed', $row['forum_flags'], $row['prune_viewed'], $row['prune_freq']);
-				}
-				else
-				{
-					auto_prune($row['forum_id'], 'viewed', $row['forum_flags'], $row['prune_viewed'], $row['prune_freq']);
-				}
-			}
-		}
-
-	break;
-}
-
-// Unloading cache and closing db after having done the dirty work.
-if ($use_shutdown_function)
-{
-	register_shutdown_function('unlock_cron');
-	register_shutdown_function('garbage_collection');
-}
-else
-{
-	unlock_cron();
+	
+	// Unloading cache and closing db after having done the dirty work.
+	$cron_lock->unlock();
 	garbage_collection();
 }
 
-exit;
+if ($cron_lock->lock()) {
+	if ($config['use_system_cron']) {
+		$use_shutdown_function = false;
+		
+		$run_tasks = $cron->find_all_runnable_tasks();
+	} else {
+		$cron_type = request_var('cron_type', '');
+		$use_shutdown_function = (@function_exists('register_shutdown_function')) ? true : false;
+		
+		output_image();
 
-
-/**
-* Unlock cron script
-*/
-function unlock_cron()
-{
-	global $db;
-
-	$sql = 'UPDATE ' . CONFIG_TABLE . "
-		SET config_value = '0'
-		WHERE config_name = 'cron_lock' AND config_value = '" . $db->sql_escape(CRON_ID) . "'";
-	$db->sql_query($sql);
+		if ($cron->is_valid_task($cron_type) && $cron->is_task_runnable($cron_type))
+		{
+			if ($use_shutdown_function && !$cron->is_task_shutdown_function_compatible($cron_type)) {
+				$use_shutdown_function = false;
+			}
+			$run_tasks = array($cron_type);
+		}
+	}
+	if ($use_shutdown_function) {
+		register_shutdown_function('do_cron', $run_tasks);
+	} else {
+		do_cron($run_tasks);
+	}
 }
diff --git a/phpBB/includes/cron.php b/phpBB/includes/cron.php
new file mode 100644
index 0000000000..2aa22858b7
--- /dev/null
+++ b/phpBB/includes/cron.php
@@ -0,0 +1,135 @@
+<?php
+/**
+*
+* @package phpBB3
+* @version $Id$
+* @copyright (c) 2010 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+* Cron class
+* @package phpBB3
+*/
+class cron
+{
+	var $tasks = array();
+	
+	function cron() {
+		global $config, $phpbb_root_path, $phpEx;
+		$modules = $config['cron_modules'];
+		$modules = explode(',', $modules);
+		foreach ($modules as $module) {
+			// explode will return array("") when exploding an empty string;
+			// users may also specify something like foo,,bar.
+			// Account for module being possibly empty
+			if (!empty($module)) {
+				// Misspelling or specifying nonexistent modules here may make the board
+				// unusable due to error messages screwing up header output
+				include_once($phpbb_root_path . "includes/cron/$module.$phpEx");
+				$cron_class = "cron_tasks_$module";
+				$object = new $cron_class;
+				foreach ($object->tasks as $cron_type => $params) {
+					$params['object'] = $object;
+					$this->tasks[$cron_type] = $params;
+				}
+			}
+		}
+	}
+	
+	function is_valid_task($cron_type) {
+		return isset($this->tasks[$cron_type]);
+	}
+	
+	function is_task_runnable($cron_type, $args=null) {
+		global $config;
+		$time_now = time();
+		$cron_params = $this->tasks[$cron_type];
+		if ($cron_params['enable_config'] && !$config[$cron_params['enable_config']]) {
+			return false;
+		}
+		if ($cron_param['custom_condition']) {
+			$callable = array($cron_params['object'], $cron_type . '_condition');
+			if ($args) {
+				$answer = call_user_func_array($callable, $args);
+			} else {
+				$answer = call_user_func($callable);
+			}
+			if (!$answer) {
+				return false;
+			}
+		}
+		if ($time_now - $config[$cron_params['interval_config']] > $config[$cron_params['last_run_config']]) {
+			return true;
+		}
+		return false;
+	}
+	
+	function is_task_shutdown_function_compatible($cron_type) {
+		$cron_params = $this->tasks[$cron_type];
+		if (isset($cron_params['shutdown_function_condition'])) {
+			return call_user_func(array($cron_params->object, $cron_type . '_shutdown_function_condition'));
+		} else {
+			return true;
+		}
+	}
+	
+	function determine_cron_mode_param() {
+		global $config;
+		if ($config['use_system_cron']) {
+			$mode = 'run_from_system';
+		} else {
+			$mode_param = 'run_from_phpbb';
+		}
+		return $mode_param;
+	}
+	
+	function find_one_runnable_task() {
+		$mode_param = $this->determine_cron_mode_param();
+		foreach ($this->tasks as $cron_type => $cron_params) {
+			if ($cron_params[$mode_param] && $this->is_task_runnable($cron_type)) {
+				return $cron_type;
+			}
+		}
+		return null;
+	}
+	
+	function find_all_runnable_tasks() {
+		$mode_param = $this->determine_cron_mode_param();
+		$tasks = array();
+		foreach ($this->tasks as $cron_type => $cron_params) {
+			if ($cron_params[$mode_param] && $this->is_task_runnable($cron_type)) {
+				$tasks[] = $cron_type;
+			}
+		}
+		return $tasks;
+	}
+	
+	function generate_task_code($cron_type, $args=array()) {
+		$cron_params = $this->tasks[$cron_type];
+		if ($cron_params['custom_code']) {
+			$code = call_user_func_array(array($cron_params['object'], $cron_type . '_code'), $args);
+		} else {
+			$code = $this->generate_generic_task_code($cron_type);
+		}
+		return $code;
+	}
+	
+	function generate_generic_task_code($cron_type) {
+		global $phpbb_root_path, $phpEx;
+		return '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=' . $cron_type) . '" width="1" height="1" alt="cron" />';
+	}
+	
+	function run_task($cron_type) {
+		call_user_func(array($this->tasks[$cron_type]['object'], 'run_' . $cron_type));
+	}
+}
diff --git a/phpBB/includes/cron/standard.php b/phpBB/includes/cron/standard.php
new file mode 100644
index 0000000000..1cb8738f17
--- /dev/null
+++ b/phpBB/includes/cron/standard.php
@@ -0,0 +1,163 @@
+<?php
+/**
+*
+* @package phpBB3
+* @version $Id$
+* @copyright (c) 2010 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+* Standard cron tasks
+* @package phpBB3
+*/
+class cron_tasks_standard
+{
+	var $tasks = array(
+		// key: cron type
+		// values: config name for enable/disable flag,
+		//         whether to check condition function to determine if the task can/should be run,
+		//         config name for interval,
+		//         config name for last run time,
+		//         whether task should be considered in phpbb cron mode,
+		//         whether task should be considered in system cron mode,
+		//         whether task requires special code generation
+		'prune_all_forums' => array(
+			'custom_condition' => true,
+			'run_from_system' => true,
+		),
+		'prune_forum' => array(
+			'custom_condition' => true,
+			'custom_code' => true,
+		),
+		'queue' => array(
+			'custom_condition' => true,
+			'interval_config' => 'queue_interval_config',
+			'last_run_config' => 'last_queue_run',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+			'shutdown_function_condition' => true,
+		),
+		'tidy_cache' => array(
+			'custom_condition' => true,
+			'interval_config' => 'cache_gc',
+			'last_run_config' => 'cache_last_gc',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+		),
+		'tidy_database' => array(
+			'interval_config' => 'database_gc',
+			'last_run_config' => 'database_last_gc',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+		),
+		'tidy_search' => array(
+			'interval_config' => 'search_gc',
+			'last_run_config' => 'search_last_gc',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+		),
+		'tidy_sessions' => array(
+			'interval_config' => 'session_gc',
+			'last_run_config' => 'session_last_gc',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+		),
+		'tidy_warnings' => array(
+			'enable_config' => 'warnings_expire_days',
+			'interval_config' => 'warnings_gc',
+			'last_run_config' => 'warnings_last_gc',
+			'run_from_phpbb' => true,
+			'run_from_system' => true,
+		),
+	);
+	
+	function prune_forum_condition($forum_data) {
+		return $forum_data['enable_prune'] && $forum_data['prune_next'] < time();
+	}
+	
+	function prune_forum_code($forum_id) {
+		global $phpbb_root_path, $phpEx;
+		return '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=prune_forum&amp;f=' . $forum_id) . '" alt="cron" width="1" height="1" />';
+	}
+	
+	function run_prune_forum() {
+	}
+	
+	function queue_condition() {
+		global $phpbb_root_path, $phpEx;
+		return file_exists($phpbb_root_path . 'cache/queue.' . $phpEx);
+	}
+	
+	function queue_shutdown_function_condition() {
+		global $config;
+		return !$config['smtp_delivery'];
+	}
+	
+	function run_queue() {
+		global $phpbb_root_path, $phpEx;
+		include_once($phpbb_root_path . 'includes/functions_messenger.' . $phpEx);
+		$queue = new queue();
+		$queue->process();
+	}
+	
+	function tidy_cache_condition() {
+		global $cache;
+		return method_exists($cache, 'tidy');
+	}
+	
+	function run_tidy_cache() {
+		global $cache;
+		$cache->tidy();
+	}
+	
+	function run_tidy_database() {
+		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
+		tidy_database();
+	}
+	
+	function tidy_search_condition() {
+		global $phpbb_root_path, $phpEx, $config;
+		
+		// Select the search method
+		$search_type = basename($config['search_type']);
+		
+		return file_exists($phpbb_root_path . 'includes/search/' . $search_type . '.' . $phpEx);
+	}
+	
+	function run_tidy_search() {
+		global $phpbb_root_path, $phpEx, $config, $error;
+		
+		// Select the search method
+		$search_type = basename($config['search_type']);
+		
+		include_once("{$phpbb_root_path}includes/search/$search_type.$phpEx");
+
+		// We do some additional checks in the module to ensure it can actually be utilised
+		$error = false;
+		$search = new $search_type($error);
+		
+		if (!$error) {
+			$search->tidy();
+		}
+	}
+	
+	function run_tidy_sessions() {
+		global $user;
+		$user->session_gc();
+	}
+	
+	function run_tidy_warnings() {
+		include_once($phpbb_root_path . 'includes/functions_admin.' . $phpEx);
+		tidy_warnings();
+	}
+}
diff --git a/phpBB/includes/cron_lock.php b/phpBB/includes/cron_lock.php
new file mode 100644
index 0000000000..2a09590772
--- /dev/null
+++ b/phpBB/includes/cron_lock.php
@@ -0,0 +1,71 @@
+<?php
+/**
+*
+* @package phpBB3
+* @version $Id$
+* @copyright (c) 2010 phpBB Group
+* @license http://opensource.org/licenses/gpl-license.php GNU Public License
+*
+*/
+
+/**
+* @ignore
+*/
+if (!defined('IN_PHPBB'))
+{
+	exit;
+}
+
+/**
+* Cron lock class
+* @package phpBB3
+*/
+class cron_lock
+{
+	function lock() {
+		global $config, $db;
+		
+		if (!isset($config['cron_lock']))
+		{
+			set_config('cron_lock', '0', true);
+		}
+
+		// make sure cron doesn't run multiple times in parallel
+		if ($config['cron_lock'])
+		{
+			// if the other process is running more than an hour already we have to assume it
+			// aborted without cleaning the lock
+			$time = explode(' ', $config['cron_lock']);
+			$time = $time[0];
+
+			if ($time + 3600 >= time())
+			{
+				return false;
+			}
+		}
+
+		define('CRON_ID', time() . ' ' . unique_id());
+
+		$sql = 'UPDATE ' . CONFIG_TABLE . "
+			SET config_value = '" . $db->sql_escape(CRON_ID) . "'
+			WHERE config_name = 'cron_lock' AND config_value = '" . $db->sql_escape($config['cron_lock']) . "'";
+		$db->sql_query($sql);
+
+		// another cron process altered the table between script start and UPDATE query so exit
+		if ($db->sql_affectedrows() != 1)
+		{
+			return false;
+		}
+		
+		return true;
+	}
+	
+	function unlock() {
+		global $db;
+
+		$sql = 'UPDATE ' . CONFIG_TABLE . "
+			SET config_value = '0'
+			WHERE config_name = 'cron_lock' AND config_value = '" . $db->sql_escape(CRON_ID) . "'";
+		$db->sql_query($sql);
+	}
+}
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 056d578e75..eb787bfc62 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -4595,7 +4595,7 @@ function page_footer($run_cron = true)
 
 	// Call cron-type script
 	$call_cron = false;
-	if (!defined('IN_CRON') && $run_cron && !$config['board_disable'])
+	if (!defined('IN_CRON') && !$config['use_system_cron'] && $run_cron && !$config['board_disable'])
 	{
 		$call_cron = true;
 		$time_now = (!empty($user->time_now) && is_int($user->time_now)) ? $user->time_now : time();
@@ -4616,40 +4616,12 @@ function page_footer($run_cron = true)
 	// Call cron job?
 	if ($call_cron)
 	{
-		$cron_type = '';
-
-		if ($time_now - $config['queue_interval'] > $config['last_queue_run'] && !defined('IN_ADMIN') && file_exists($phpbb_root_path . 'cache/queue.' . $phpEx))
-		{
-			// Process email queue
-			$cron_type = 'queue';
-		}
-		else if (method_exists($cache, 'tidy') && $time_now - $config['cache_gc'] > $config['cache_last_gc'])
-		{
-			// Tidy the cache
-			$cron_type = 'tidy_cache';
-		}
-		else if ($config['warnings_expire_days'] && ($time_now - $config['warnings_gc'] > $config['warnings_last_gc']))
-		{
-			$cron_type = 'tidy_warnings';
-		}
-		else if ($time_now - $config['database_gc'] > $config['database_last_gc'])
-		{
-			// Tidy the database
-			$cron_type = 'tidy_database';
-		}
-		else if ($time_now - $config['search_gc'] > $config['search_last_gc'])
-		{
-			// Tidy the search
-			$cron_type = 'tidy_search';
-		}
-		else if ($time_now - $config['session_gc'] > $config['session_last_gc'])
-		{
-			$cron_type = 'tidy_sessions';
-		}
+		global $cron;
+		$cron_type = $cron->find_one_runnable_task();
 
 		if ($cron_type)
 		{
-			$template->assign_var('RUN_CRON_TASK', '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=' . $cron_type) . '" width="1" height="1" alt="cron" />');
+			$template->assign_var('RUN_CRON_TASK', $cron->generate_task_code($cron_type));
 		}
 	}
 
diff --git a/phpBB/viewforum.php b/phpBB/viewforum.php
index 47d71849cb..8a06e28394 100644
--- a/phpBB/viewforum.php
+++ b/phpBB/viewforum.php
@@ -193,9 +193,9 @@ if ($forum_data['forum_topics_per_page'])
 }
 
 // Do the forum Prune thang - cron type job ...
-if ($forum_data['prune_next'] < time() && $forum_data['enable_prune'])
+if (!$config['use_system_cron'] && $cron->is_task_runnable('prune_forum', array($forum_data)))
 {
-	$template->assign_var('RUN_CRON_TASK', '<img src="' . append_sid($phpbb_root_path . 'cron.' . $phpEx, 'cron_type=prune_forum&amp;f=' . $forum_id) . '" alt="cron" width="1" height="1" />');
+	$template->assign_var('RUN_CRON_TASK', $cron->generate_task_code('prune_forum', array($forum_id)));
 }
 
 // Forum rules and subscription info