Fix #4093
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index 7f33347..cf1100d 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -2342,7 +2342,7 @@
 
 				// Split multiple conditions
 				$conditions = preg_split(
-					'/((^|\s+)AND\s+|(^|\s+)OR\s+)/i',
+					'/((?:^|\s+)AND\s+|(?:^|\s+)OR\s+)/i',
 					$this->{$qb_key}[$i]['condition'],
 					-1,
 					PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY