Though I planned to refactor tbl_structure.php this week, I couldn't do much of it due to some reasons. Instead I refactored the tbl_create.php and tbl_tracking.php. I was able to refactor the tbl_create.php by using extract method and removing some dead code. And in tbl_tracking.php I was able to extract several methods which are responsible for generating the html output into a new script file called tbl_tracking.lib.php.
My plan for this week is to complete refactoring the tbl_structure.php file and complete refactoring the tbl_tracking.php file.