通过PHP MYSQL页面传递多个变量

The following code is working fine for the first page. It is a query based on user input from a form. I have 2 issues. The first one is when i click next page i get undefined index and undefined variable error which means the variables are not passed. The second question is how can i make a query and paginate it based on the user filled/selected values in the form? Some users may not fill all the values. Here is my code: NB: The form method is GET. I have tried REQUEST and POST too. All the same error. Thanks in advance guys.The following code is working fine for the firs