Part 9: Error Handling and Chaining From Page to Page

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Part 9: Error Handing and Chaining From Page to Page

The example introduced the subroutine PLW.PAGE(...,...,...) and used this subroutine to chain to error pages. PLW.PAGE is actually the main PicLan-IP web server subroutine that is used to process a page transaction. When you call PLW.PAGE, you are actually recursively calling the subroutine that is itself calling your program. This operation give you great flexibility in controlling page flow. The important thing to remember about calling PLW.PAGE is that you will usually want to include a RETURN statement so that the new pages result will be used and not the merge results from the current page.

Because of the way that PLW.PAGE(...) allows you to chain from page to page, may web designers choose to build a PicLan-IP web application using the same page name for all of the pages. The logic within this main page then reads variables and branches to other pages depending on the applications current status. While this may seem confusing, it effectively prevents the user from bookmarking an application mid-stream and insures that users always start at the beginning.

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