1. $sql_ary is an array and not the string in core.obtain_users_online_string_sql.
https://github.com/RMcGirr83/phpbb/commit/8a52ccc9389dd54e42e357f09808203dcbf65e91#commitcomment-15448145
2. $sql_ary is an array and not the integer in core.mcp_front_queue_unapproved_total_before.
3. Other occurrences.