diff --git a/phpBB/adm/style/acp_search_index_inprogress.html b/phpBB/adm/style/acp_search_index_inprogress.html
index b8206c8d46..0f2c2e6f77 100644
--- a/phpBB/adm/style/acp_search_index_inprogress.html
+++ b/phpBB/adm/style/acp_search_index_inprogress.html
@@ -4,6 +4,7 @@
 
 <h1>{L_ACP_SEARCH_INDEX}</h1>
 
+{# todo: check the l_continue that is send from acp_search here #}
 <p>{L_CONTINUE_EXPLAIN}</p>
 
 <form id="acp_search_continue" method="post" action="{U_CONTINUE_INDEXING}">
diff --git a/phpBB/includes/acp/acp_search.php b/phpBB/includes/acp/acp_search.php
index 2d73913ac1..a3a304bb62 100644
--- a/phpBB/includes/acp/acp_search.php
+++ b/phpBB/includes/acp/acp_search.php
@@ -14,6 +14,16 @@
 /**
 * @ignore
 */
+
+use phpbb\config\config;
+use phpbb\di\service_collection;
+use phpbb\language\language;
+use phpbb\log\log;
+use phpbb\request\request;
+use phpbb\search\search_backend_factory;
+use phpbb\template\template;
+use phpbb\user;
+
 if (!defined('IN_PHPBB'))
 {
 	exit;
@@ -22,19 +32,88 @@ if (!defined('IN_PHPBB'))
 class acp_search
 {
 	public $u_action;
+	public $tpl_name;
+	public $page_title;
 
 	protected const STATE_SEARCH_TYPE = 0;
 	protected const STATE_ACTION = 1;
 	protected const STATE_POST_COUNTER = 2;
 
-	public function main($id, $mode)
+	/**
+	 * @var config
+	 */
+	protected $config;
+
+	/**
+	 * @var language
+	 */
+	protected $language;
+
+	/**
+	 * @var log
+	 */
+	protected $log;
+
+	/**
+	 * @var request
+	 */
+	protected $request;
+
+	/**
+	 * @var service_collection
+	 */
+	protected $search_backend_collection;
+
+	/**
+	 * @var search_backend_factory
+	 */
+	protected $search_backend_factory;
+
+	/**
+	 * @var template
+	 */
+	protected $template;
+
+	/**
+	 * @var user
+	 */
+	protected $user;
+
+	/**
+	 * @var string
+	 */
+	protected $phpbb_admin_path;
+
+	/**
+	 * @var string
+	 */
+	protected $php_ex;
+
+	public function __construct($p_master)
 	{
-		global $user;
+		global $config, $phpbb_container, $language, $phpbb_log, $request, $template, $user, $phpbb_admin_path, $phpEx;
 
-		$user->add_lang('acp/search');
+		$this->config = $config;
+		$this->language = $language;
+		$this->log = $phpbb_log;
+		$this->request = $request;
+		$this->search_backend_collection = $phpbb_container->get('search.backend_collection');
+		$this->search_backend_factory = $phpbb_container->get('search.backend_factory');
+		$this->template = $template;
+		$this->user = $user;
+		$this->phpbb_admin_path = $phpbb_admin_path;
+		$this->php_ex = $phpEx;
+	}
 
-		// For some this may be of help...
-		@ini_set('memory_limit', '128M');
+	/**
+	 * @param string $id
+	 * @param string $mode
+	 * @throws Exception
+	 * @return void
+	 */
+	public function main(string $id, string $mode): void
+	{
+		$this->language->add_lang('acp/search');
 
 		switch ($mode)
 		{
@@ -48,21 +127,15 @@ class acp_search
 		}
 	}
 
-	function settings($id, $mode)
+	public function settings(string $id, string $mode): void
 	{
-		global $user, $template, $phpbb_log, $request;
-		global $config, $phpbb_admin_path, $phpEx;
-		global $phpbb_container;
+		$submit = $this->request->is_set_post('submit');
 
-		$submit = $request->is_set_post('submit');
-
-		if ($submit && !check_link_hash($request->variable('hash', ''), 'acp_search'))
+		if ($submit && !check_link_hash($this->request->variable('hash', ''), 'acp_search'))
 		{
-			trigger_error($user->lang['FORM_INVALID'] . adm_back_link($this->u_action), E_USER_WARNING);
+			trigger_error($this->language->lang('FORM_INVALID') . adm_back_link($this->u_action), E_USER_WARNING);
 		}
 
-		$search_types = $phpbb_container->get('search.backend_collection');
-
 		$settings = [
 			'search_interval'				=> 'float',
 			'search_anonymous_interval'		=> 'float',
@@ -74,18 +147,17 @@ class acp_search
 			'search_store_results'			=> 'integer',
 		];
 
-		$search = null;
 		$search_options = '';
 
-		foreach ($search_types as $search)
+		foreach ($this->search_backend_collection as $search)
 		{
 			// Only show available search backends
 			if ($search->is_available())
 			{
 				$name = $search->get_name();
-				$type = get_class($search);
+				$type = $search->get_type();
 
-				$selected = ($config['search_type'] == $type) ? ' selected="selected"' : '';
+				$selected = ($this->config['search_type'] == $type) ? ' selected="selected"' : '';
 				$identifier = substr($type, strrpos($type, '\\') + 1);
 				$search_options .= "<option value=\"$type\"$selected data-toggle-setting=\"#search_{$identifier}_settings\">$name</option>";
 
@@ -93,7 +165,7 @@ class acp_search
 
 				if (!$submit)
 				{
-					$template->assign_block_vars('backend', array(
+					$this->template->assign_block_vars('backend', array(
 						'NAME' => $name,
 						'SETTINGS' => $vars['tpl'],
 						'IDENTIFIER' => $identifier,
@@ -105,14 +177,13 @@ class acp_search
 				}
 			}
 		}
-		unset($search);
 
-		$cfg_array = (isset($_REQUEST['config'])) ? $request->variable('config', array('' => ''), true) : array();
-		$updated = $request->variable('updated', false);
+		$cfg_array = (isset($_REQUEST['config'])) ? $this->request->variable('config', array('' => ''), true) : array();
+		$updated = $this->request->variable('updated', false);
 
-		foreach ($settings as $config_name => $var_type)
+		foreach ($settings as $this->config_name => $var_type)
 		{
-			if (!isset($cfg_array[$config_name]))
+			if (!isset($cfg_array[$this->config_name]))
 			{
 				continue;
 			}
@@ -120,23 +191,23 @@ class acp_search
 			// e.g. integer:4:12 (min 4, max 12)
 			$var_type = explode(':', $var_type);
 
-			$config_value = $cfg_array[$config_name];
-			settype($config_value, $var_type[0]);
+			$this->config_value = $cfg_array[$this->config_name];
+			settype($this->config_value, $var_type[0]);
 
 			if (isset($var_type[1]))
 			{
-				$config_value = max($var_type[1], $config_value);
+				$this->config_value = max($var_type[1], $this->config_value);
 			}
 
 			if (isset($var_type[2]))
 			{
-				$config_value = min($var_type[2], $config_value);
+				$this->config_value = min($var_type[2], $this->config_value);
 			}
 
 			// only change config if anything was actually changed
-			if ($submit && ($config[$config_name] != $config_value))
+			if ($submit && ($this->config[$this->config_name] != $this->config_value))
 			{
-				$config->set($config_name, $config_value);
+				$this->config->set($this->config_name, $this->config_value);
 				$updated = true;
 			}
 		}
@@ -146,25 +217,24 @@ class acp_search
 			$extra_message = '';
 			if ($updated)
 			{
-				$phpbb_log->add('admin', $user->data['user_id'], $user->ip, 'LOG_CONFIG_SEARCH');
+				$this->log->add('admin', $this->user->data['user_id'], $this->user->ip, 'LOG_CONFIG_SEARCH');
 			}
 
-			if (isset($cfg_array['search_type']) && ($cfg_array['search_type'] != $config['search_type']))
+			if (isset($cfg_array['search_type']) && ($cfg_array['search_type'] != $this->config['search_type']))
 			{
-				$search_backend_factory = $phpbb_container->get('search.backend_factory');
-				$search = $search_backend_factory->get($cfg_array['search_type']);
+				$search = $this->search_backend_factory->get($cfg_array['search_type']);
 				if (confirm_box(true))
 				{
 					// Initialize search backend, if $error is false means that everything is ok
 					if (!($error = $search->init()))
 					{
-						$config->set('search_type', $cfg_array['search_type']);
+						$this->config->set('search_type', $cfg_array['search_type']);
 
 						if (!$updated)
 						{
-							$phpbb_log->add('admin', $user->data['user_id'], $user->ip, 'LOG_CONFIG_SEARCH');
+							$this->log->add('admin', $this->user->data['user_id'], $this->user->ip, 'LOG_CONFIG_SEARCH');
 						}
-						$extra_message = '<br />' . $user->lang['SWITCHED_SEARCH_BACKEND'] . '<br /><a href="' . append_sid("{$phpbb_admin_path}index.$phpEx", 'i=search&amp;mode=index') . '">&raquo; ' . $user->lang['GO_TO_SEARCH_INDEX'] . '</a>';
+						$extra_message = '<br />' . $this->language->lang('SWITCHED_SEARCH_BACKEND') . '<br /><a href="' . append_sid($this->phpbb_admin_path . "index." . $this->php_ex, 'i=search&amp;mode=index') . '">&raquo; ' . $this->language->lang('GO_TO_SEARCH_INDEX') . '</a>';
 					}
 					else
 					{
@@ -173,7 +243,7 @@ class acp_search
 				}
 				else
 				{
-					confirm_box(false, $user->lang['CONFIRM_SEARCH_BACKEND'], build_hidden_fields(array(
+					confirm_box(false, $this->language->lang('CONFIRM_SEARCH_BACKEND'), build_hidden_fields(array(
 						'i'			=> $id,
 						'mode'		=> $mode,
 						'submit'	=> true,
@@ -183,215 +253,248 @@ class acp_search
 				}
 			}
 
-			trigger_error($user->lang['CONFIG_UPDATED'] . $extra_message . adm_back_link($this->u_action));
+			trigger_error($this->language->lang('CONFIG_UPDATED') . $extra_message . adm_back_link($this->u_action));
 		}
 		unset($cfg_array);
 
 		$this->tpl_name = 'acp_search_settings';
 		$this->page_title = 'ACP_SEARCH_SETTINGS';
 
-		$template->assign_vars([
-			'DEFAULT_SEARCH_RETURN_CHARS'	=> (int) $config['default_search_return_chars'],
-			'LIMIT_SEARCH_LOAD'				=> (float) $config['limit_search_load'],
-			'MIN_SEARCH_AUTHOR_CHARS'		=> (int) $config['min_search_author_chars'],
-			'SEARCH_INTERVAL'				=> (float) $config['search_interval'],
-			'SEARCH_GUEST_INTERVAL'			=> (float) $config['search_anonymous_interval'],
-			'SEARCH_STORE_RESULTS'			=> (int) $config['search_store_results'],
-			'MAX_NUM_SEARCH_KEYWORDS'		=> (int) $config['max_num_search_keywords'],
+		$this->template->assign_vars([
+			'DEFAULT_SEARCH_RETURN_CHARS'	=> (int) $this->config['default_search_return_chars'],
+			'LIMIT_SEARCH_LOAD'				=> (float) $this->config['limit_search_load'],
+			'MIN_SEARCH_AUTHOR_CHARS'		=> (int) $this->config['min_search_author_chars'],
+			'SEARCH_INTERVAL'				=> (float) $this->config['search_interval'],
+			'SEARCH_GUEST_INTERVAL'			=> (float) $this->config['search_anonymous_interval'],
+			'SEARCH_STORE_RESULTS'			=> (int) $this->config['search_store_results'],
+			'MAX_NUM_SEARCH_KEYWORDS'		=> (int) $this->config['max_num_search_keywords'],
 
 			'S_SEARCH_TYPES'		=> $search_options,
-			'S_YES_SEARCH'			=> (bool) $config['load_search'],
+			'S_YES_SEARCH'			=> (bool) $this->config['load_search'],
 
 			'U_ACTION'				=> $this->u_action . '&amp;hash=' . generate_link_hash('acp_search'),
 		]);
 	}
 
-	public function index($id, $mode)
+	/**
+	 * @param string $id
+	 * @param string $mode
+	 * @throws Exception
+	 */
+	public function index(string $id, string $mode): void
 	{
-		global $user, $template, $phpbb_log, $request;
-		global $config, $phpbb_admin_path, $phpEx, $phpbb_container;
+		$action = $this->request->variable('action', '');
+		$state = !empty($this->config['search_indexing_state']) ? explode(',', $this->config['search_indexing_state']) : [];
 
-		$action = $request->variable('action', '');
-		$state = explode(',', $config['search_indexing_state']);
-
-		if ($request->is_set_post('cancel'))
-		{
-			$action = '';
-			$state = array();
-			$this->save_state($state);
-		}
-		$submit = $request->is_set_post('submit');
-
-		if (!check_link_hash($request->variable('hash', ''), 'acp_search') && in_array($action, array('create', 'delete')))
-		{
-			trigger_error($user->lang['FORM_INVALID'] . adm_back_link($this->u_action), E_USER_WARNING);
-		}
-
-		if ($action)
+		if($action)
 		{
 			switch ($action)
 			{
 				case 'progress_bar':
-					$type = $request->variable('type', '');
-					$this->display_progress_bar($type);
-				break;
-
-				case 'delete':
-					$state[self::STATE_ACTION] = 'delete';
+					$this->display_progress_bar();
 				break;
 
 				case 'create':
-					$state[self::STATE_ACTION] = 'create';
+				case 'delete':
+					$this->index_action($id, $mode, $action, $state);
 				break;
 
 				default:
 					trigger_error('NO_ACTION', E_USER_ERROR);
 			}
-
-			if (empty($state[self::STATE_SEARCH_TYPE]))
+		}
+		else
+		{
+			// If clicked to no continue with the indexing progress (acp_search_index_inprogress form)
+			if ($this->request->is_set_post('cancel'))
 			{
-				$state[self::STATE_SEARCH_TYPE] = $request->variable('search_type', '');
+				$state = [];
+				$this->save_state($state);
 			}
 
-			$search_backend_factory = $phpbb_container->get('search.backend_factory');
-			$search = $search_backend_factory->get($state[self::STATE_SEARCH_TYPE]);
-
-			$name = $search->get_name();
-
-			$action = &$state[1];
-
-			$this->save_state($state);
-
-			switch ($action)
+			if (!empty($state))
 			{
-				case 'delete':
-					try
-					{
-						$state[self::STATE_POST_COUNTER] = $state[self::STATE_POST_COUNTER] ?? 0;
-						if ($status = $search->delete_index($state[self::STATE_POST_COUNTER])) // Status is not null, so deleting is in progress....
-						{
-							// save the current state
-							$this->save_state($state);
-
-							$u_action = append_sid("{$phpbb_admin_path}index.$phpEx", "i=$id&mode=$mode&action=delete&hash=" . generate_link_hash('acp_search'), false);
-							meta_refresh(1, $u_action);
-							trigger_error($user->lang('SEARCH_INDEX_DELETE_REDIRECT', (int) $status['row_count'], $status['post_counter']) . $user->lang('SEARCH_INDEX_DELETE_REDIRECT_RATE', $status['rows_per_second']));
-						}
-					}
-					catch (Exception $e)
-					{
-						$state = [];
-						$this->save_state($state);
-						trigger_error($e->getMessage() . adm_back_link($this->u_action) . $this->close_popup_js(), E_USER_WARNING);
-					}
-
-					$search->tidy();
-
-					$state = [];
-					$this->save_state($state);
-
-					$phpbb_log->add('admin', $user->data['user_id'], $user->ip, 'LOG_SEARCH_INDEX_REMOVED', false, array($name));
-					trigger_error($user->lang['SEARCH_INDEX_REMOVED'] . adm_back_link($this->u_action) . $this->close_popup_js());
-				break;
-
-				case 'create':
-					try
-					{
-						$state[self::STATE_POST_COUNTER] = $state[self::STATE_POST_COUNTER] ?? 0;
-						if ($status = $search->create_index($state[self::STATE_POST_COUNTER])) // Status is not null, so indexing is in progress....
-						{
-							// save the current state
-							$this->save_state($state);
-
-							$u_action = append_sid("{$phpbb_admin_path}index.$phpEx", "i=$id&mode=$mode&action=create&hash=" . generate_link_hash('acp_search'), false);
-							meta_refresh(1, $u_action);
-							trigger_error($user->lang('SEARCH_INDEX_CREATE_REDIRECT', (int) $status['row_count'], $status['post_counter']) . $user->lang('SEARCH_INDEX_CREATE_REDIRECT_RATE', $status['rows_per_second']));
-						}
-					}
-					catch (Exception $e)
-					{
-						// Error executing create_index
-						$state = [];
-						$this->save_state($state);
-						trigger_error($e->getMessage() . adm_back_link($this->u_action) . $this->close_popup_js(), E_USER_WARNING);
-					}
-
-					// Indexing have finished
-
-					$search->tidy();
-
-					$state = [];
-					$this->save_state($state);
-
-					$phpbb_log->add('admin', $user->data['user_id'], $user->ip, 'LOG_SEARCH_INDEX_CREATED', false, array($name));
-					trigger_error($user->lang['SEARCH_INDEX_CREATED'] . adm_back_link($this->u_action) . $this->close_popup_js());
-				break;
+				$this->index_inprogress($id, $mode, $state[self::STATE_ACTION]);
+			}
+			else
+			{
+				$this->index_overview($id, $mode);
 			}
-		}
-
-		$search_types = $phpbb_container->get('search.backend_collection');
-
-		foreach ($search_types as $search)
-		{
-			$type = get_class($search);
-			$name = $search->get_name();
-			$data =  $search->index_stats();
-
-			$template->assign_block_vars('backend', array(
-				'L_NAME'			=> $name,
-				'NAME'				=> $type,
-
-				'S_ACTIVE'			=> $type == $config['search_type'],
-				'S_HIDDEN_FIELDS'	=> build_hidden_fields(array('search_type' => $type)),
-				'S_INDEXED'			=> (bool) $search->index_created(),
-				'S_STATS'			=> $data,
-			));
-		}
-
-		$this->tpl_name = 'acp_search_index';
-		$this->page_title = 'ACP_SEARCH_INDEX';
-
-		$template->assign_vars(array(
-			'U_ACTION'				=> $this->u_action . '&amp;hash=' . generate_link_hash('acp_search'),
-			'U_PROGRESS_BAR'		=> append_sid("{$phpbb_admin_path}index.$phpEx", "i=$id&amp;mode=$mode&amp;action=progress_bar"),
-			'UA_PROGRESS_BAR'		=> addslashes(append_sid("{$phpbb_admin_path}index.$phpEx", "i=$id&amp;mode=$mode&amp;action=progress_bar")),
-		));
-
-		if (isset($state[self::STATE_ACTION]))
-		{
-			$this->tpl_name = 'acp_search_index';
-			$this->page_title = 'ACP_SEARCH_INDEX';
-
-			$template->assign_vars(array(
-				'S_CONTINUE_INDEXING'	=> $state[1],
-				'U_CONTINUE_INDEXING'	=> $this->u_action . '&amp;action=' . $state[self::STATE_ACTION] . '&amp;hash=' . generate_link_hash('acp_search'),
-				'L_CONTINUE'			=> ($state[self::STATE_ACTION] == 'create') ? $user->lang['CONTINUE_INDEXING'] : $user->lang['CONTINUE_DELETING_INDEX'],
-				'L_CONTINUE_EXPLAIN'	=> ($state[self::STATE_ACTION] == 'create') ? $user->lang['CONTINUE_INDEXING_EXPLAIN'] : $user->lang['CONTINUE_DELETING_INDEX_EXPLAIN'])
-			);
 		}
 	}
 
-	function display_progress_bar($type)
+	/**
+	 * @param string $id
+	 * @param string $mode
+	 *
+	 * @throws Exception
+	 */
+	private function index_overview(string $id, string $mode): void
 	{
-		global $template, $user;
+		$this->tpl_name = 'acp_search_index';
+		$this->page_title = 'ACP_SEARCH_INDEX';
 
-		$l_type = ($type == 'create') ? 'INDEXING_IN_PROGRESS' : 'DELETING_INDEX_IN_PROGRESS';
+		foreach ($this->search_backend_collection as $search)
+		{
+			$this->template->assign_block_vars('backend', array(
+				'L_NAME'			=> $search->get_name(),
+				'NAME'				=> $search->get_type(),
 
-		adm_page_header($user->lang[$l_type]);
+				'S_ACTIVE'			=> $search->get_type() === $this->config['search_type'],
+				'S_HIDDEN_FIELDS'	=> build_hidden_fields(array('search_type' => $search->get_type())),
+				'S_INDEXED'			=> $search->index_created(),
+				'S_STATS'			=> $search->index_stats(),
+			));
+		}
 
-		$template->set_filenames(array(
+		$this->template->assign_vars(array(
+			'U_ACTION'				=> $this->u_action . '&amp;hash=' . generate_link_hash('acp_search'),
+			'UA_PROGRESS_BAR'		=> addslashes($this->u_action . '&amp;action=progress_bar'),
+		));
+	}
+
+	/**
+	 * Form to continue or cancel indexing process
+	 *
+	 * @param string $id
+	 * @param string $mode
+	 * @param string $action Action in progress: 'create' or 'delete'
+	 */
+	private function index_inprogress(string $id, string $mode, string $action): void
+	{
+		$this->tpl_name = 'acp_search_inprogress';
+		$this->page_title = 'ACP_SEARCH_INDEX';
+
+		$this->template->assign_vars(array(
+			'U_CONTINUE_INDEXING'	=> $this->u_action . '&amp;action=' . $action . '&amp;hash=' . generate_link_hash('acp_search'),
+			'L_CONTINUE'			=> ($action === 'create') ? $this->language->lang('CONTINUE_INDEXING') : $this->language->lang('CONTINUE_DELETING_INDEX'),
+			'L_CONTINUE_EXPLAIN'	=> ($action === 'create') ? $this->language->lang('CONTINUE_INDEXING_EXPLAIN') : $this->language->lang('CONTINUE_DELETING_INDEX_EXPLAIN'))
+		);
+	}
+
+	private function index_action(string $id, string $mode, string $action, array $state): void
+	{
+		// For some this may be of help...
+		@ini_set('memory_limit', '128M');
+
+		if (!check_link_hash($this->request->variable('hash', ''), 'acp_search'))
+		{
+			trigger_error($this->language->lang('FORM_INVALID') . adm_back_link($this->u_action), E_USER_WARNING);
+		}
+
+		// Entering here for the first time
+		if (empty($state))
+		{
+			if ($this->request->is_set_post('search_type', '')) {
+				$state = [
+					self::STATE_SEARCH_TYPE => $this->request->variable('search_type', ''),
+					self::STATE_ACTION => $action,
+					self::STATE_POST_COUNTER => 0
+				];
+			}
+			else
+			{
+				trigger_error($this->language->lang('FORM_INVALID') . adm_back_link($this->u_action), E_USER_WARNING);
+			}
+
+			$this->save_state($state); // Create new state in the database
+		}
+
+		$type = $state[self::STATE_SEARCH_TYPE];
+		$action = $state[self::STATE_ACTION];
+		$post_counter = &$state[self::STATE_POST_COUNTER];
+
+		switch ($action)
+		{
+			case 'delete':
+				$search = $this->search_backend_factory->get($type);
+
+				try
+				{
+					if ($status = $search->delete_index($post_counter)) // Status is not null, so deleting is in progress....
+					{
+						$this->save_state($state); // update $post_counter in $state in the database
+
+						$u_action = append_sid($this->phpbb_admin_path . "index." . $this->php_ex, "i=$id&mode=$mode&action=delete&hash=" . generate_link_hash('acp_search'), false);
+						meta_refresh(1, $u_action);
+						trigger_error($this->language->lang('SEARCH_INDEX_DELETE_REDIRECT', (int) $status['row_count'], $status['post_counter']) . $this->language->lang('SEARCH_INDEX_DELETE_REDIRECT_RATE', $status['rows_per_second']));
+					}
+				}
+				catch (Exception $e)
+				{
+					$this->save_state([]); // Unexpected error, cancel action
+					trigger_error($e->getMessage() . adm_back_link($this->u_action) . $this->close_popup_js(), E_USER_WARNING);
+				}
+
+				$search->tidy();
+
+				$this->save_state([]); // finished operation, cancel action
+
+				$this->log->add('admin', $this->user->data['user_id'], $this->user->ip, 'LOG_SEARCH_INDEX_REMOVED', false, array($search->get_name()));
+				trigger_error($this->language->lang('SEARCH_INDEX_REMOVED') . adm_back_link($this->u_action) . $this->close_popup_js());
+			break;
+
+			case 'create':
+				$search = $this->search_backend_factory->get($type);
+
+				try
+				{
+					$search = $this->search_backend_factory->get($type);
+
+					if ($status = $search->create_index($post_counter)) // Status is not null, so indexing is in progress....
+					{
+						$this->save_state($state); // update $post_counter in $state in the database
+
+						$u_action = append_sid($this->phpbb_admin_path . "index." . $this->php_ex, "i=$id&mode=$mode&action=create&hash=" . generate_link_hash('acp_search'), false);
+						meta_refresh(1, $u_action);
+						trigger_error($this->language->lang('SEARCH_INDEX_CREATE_REDIRECT', (int) $status['row_count'], $status['post_counter']) . $this->language->lang('SEARCH_INDEX_CREATE_REDIRECT_RATE', $status['rows_per_second']));
+					}
+				}
+				catch (Exception $e)
+				{
+					// Error executing create_index
+					$this->save_state([]);
+					trigger_error($e->getMessage() . adm_back_link($this->u_action) . $this->close_popup_js(), E_USER_WARNING);
+				}
+
+				$search->tidy();
+
+				$this->save_state([]); // finished operation, cancel action
+
+				$this->log->add('admin', $this->user->data['user_id'], $this->user->ip, 'LOG_SEARCH_INDEX_CREATED', false, array($search->get_name()));
+				trigger_error($this->language->lang('SEARCH_INDEX_CREATED') . adm_back_link($this->u_action) . $this->close_popup_js());
+			break;
+		}
+	}
+
+	/**
+	 * Popup window
+	 */
+	private function display_progress_bar(): void
+	{
+		$type = $this->request->variable('type', '');
+		$l_type = ($type === 'create') ? 'INDEXING_IN_PROGRESS' : 'DELETING_INDEX_IN_PROGRESS';
+
+		adm_page_header($this->language->lang($l_type));
+
+		$this->template->set_filenames(array(
 			'body'	=> 'progress_bar.html')
 		);
 
-		$template->assign_vars(array(
-			'L_PROGRESS'			=> $user->lang[$l_type],
-			'L_PROGRESS_EXPLAIN'	=> $user->lang[$l_type . '_EXPLAIN'])
-		);
+		$this->template->assign_vars(array(
+			'L_PROGRESS'			=> $this->language->lang($l_type),
+			'L_PROGRESS_EXPLAIN'	=> $this->language->lang($l_type . '_EXPLAIN'),
+		));
 
 		adm_page_footer();
 	}
 
-	function close_popup_js()
+	/**
+	 * Javascript code for closing the waiting screen (is attached to the trigger_errors)
+	 *
+	 * @return string
+	 */
+	private function close_popup_js(): string
 	{
 		return "<script type=\"text/javascript\">\n" .
 			"// <![CDATA[\n" .
@@ -400,12 +503,13 @@ class acp_search
 			"</script>\n";
 	}
 
-	function save_state($state = false)
+	/**
+	 * @param array $state
+	 */
+	private function save_state(array $state = []): void
 	{
-		global $config;
-
 		ksort($state);
 
-		$config->set('search_indexing_state', implode(',', $state), true);
+		$this->config->set('search_indexing_state', implode(',', $state), true);
 	}
 }
diff --git a/phpBB/phpbb/search/backend/base.php b/phpBB/phpbb/search/backend/base.php
index 0245c72c2a..a6bcb08850 100644
--- a/phpBB/phpbb/search/backend/base.php
+++ b/phpBB/phpbb/search/backend/base.php
@@ -480,4 +480,12 @@ abstract class base implements search_backend_interface
 
 		return $max_post_id;
 	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function get_type(): string
+	{
+		return static::class;
+	}
 }
diff --git a/phpBB/phpbb/search/backend/fulltext_sphinx.php b/phpBB/phpbb/search/backend/fulltext_sphinx.php
index cc6c0b8afe..1d7ff5f310 100644
--- a/phpBB/phpbb/search/backend/fulltext_sphinx.php
+++ b/phpBB/phpbb/search/backend/fulltext_sphinx.php
@@ -1022,4 +1022,12 @@ class fulltext_sphinx implements search_backend_interface
 
 		return true;
 	}
+
+	/**
+	 * {@inheritdoc}
+	 */
+	public function get_type(): string
+	{
+		return static::class;
+	}
 }
diff --git a/phpBB/phpbb/search/backend/search_backend_interface.php b/phpBB/phpbb/search/backend/search_backend_interface.php
index 1fdc138028..82ea0d03ff 100644
--- a/phpBB/phpbb/search/backend/search_backend_interface.php
+++ b/phpBB/phpbb/search/backend/search_backend_interface.php
@@ -193,4 +193,11 @@ interface search_backend_interface
 	 * @return array array containing template and config variables
 	 */
 	public function get_acp_options(): array;
+
+	/**
+	 * Gets backend class
+	 *
+	 * @return string
+	 */
+	public function get_type(): string;
 }
diff --git a/phpBB/phpbb/storage/provider/local.php b/phpBB/phpbb/storage/provider/local.php
index 8e0de2b6fd..93d3c7a6d0 100644
--- a/phpBB/phpbb/storage/provider/local.php
+++ b/phpBB/phpbb/storage/provider/local.php
@@ -26,7 +26,7 @@ class local implements provider_interface
 	/**
 	 * {@inheritdoc}
 	 */
-	public function get_adapter_class()
+	public function get_adapter_class(): string
 	{
 		return \phpbb\storage\adapter\local::class;
 	}
diff --git a/phpBB/phpbb/storage/provider/provider_interface.php b/phpBB/phpbb/storage/provider/provider_interface.php
index 428b6eb187..484b660aa8 100644
--- a/phpBB/phpbb/storage/provider/provider_interface.php
+++ b/phpBB/phpbb/storage/provider/provider_interface.php
@@ -25,9 +25,9 @@ interface provider_interface
 	/**
 	 * Gets adapter class
 	 *
-	 * @return \phpbb\storage\adapter\adapter_interface
+	 * @return string
 	 */
-	public function get_adapter_class();
+	public function get_adapter_class(): string;
 
 	/**
 	 * Gets adapter options