diff --git a/.travis.yml b/.travis.yml
index 2049a2f6f8..699c4ecac6 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -20,11 +20,14 @@ matrix:
       env: DB=mysqli
     - php: 7.0
       env: DB=mysqli
+    - php: 7.1
+      env: DB=mysqli
     - php: nightly
       env: DB=mysqli
     - php: hhvm
       env: DB=mysqli
   allow_failures:
+    - php: 7.1
     - php: hhvm
     - php: nightly
   fast_finish: true
diff --git a/phpBB/includes/functions.php b/phpBB/includes/functions.php
index 9994e874a6..946b3b0ff7 100644
--- a/phpBB/includes/functions.php
+++ b/phpBB/includes/functions.php
@@ -841,7 +841,7 @@ function markread($mode, $forum_id = false, $topic_id = false, $post_time = 0, $
 				$tracking['tf'][$forum_id][$topic_id36] = true;
 			}
 
-			$tracking['t'][$topic_id36] = base_convert($post_time - $config['board_startdate'], 10, 36);
+			$tracking['t'][$topic_id36] = base_convert($post_time - (int) $config['board_startdate'], 10, 36);
 
 			// If the cookie grows larger than 10000 characters we will remove the smallest value
 			// This can result in old topics being unread - but most of the time it should be accurate...
diff --git a/phpBB/phpbb/db/migration/data/v310/timezone.php b/phpBB/phpbb/db/migration/data/v310/timezone.php
index 1f6b47ad50..03a8d1ab34 100644
--- a/phpBB/phpbb/db/migration/data/v310/timezone.php
+++ b/phpBB/phpbb/db/migration/data/v310/timezone.php
@@ -103,7 +103,7 @@ class timezone extends \phpbb\db\migration\migration
 	*/
 	public function convert_phpbb30_timezone($timezone, $dst)
 	{
-		$offset = $timezone + $dst;
+		$offset = (float) $timezone + (int) $dst;
 
 		switch ($timezone)
 		{
diff --git a/phpBB/phpbb/search/base.php b/phpBB/phpbb/search/base.php
index d9313dddab..56de973b65 100644
--- a/phpBB/phpbb/search/base.php
+++ b/phpBB/phpbb/search/base.php
@@ -286,7 +286,7 @@ class base
 
 		$sql = 'DELETE
 			FROM ' . SEARCH_RESULTS_TABLE . '
-			WHERE search_time < ' . (time() - $config['search_store_results']);
+			WHERE search_time < ' . (time() - (int) $config['search_store_results']);
 		$db->sql_query($sql);
 	}
 }