A Viewstate for PHP

One of the ASP. Attractive features is the viewstate. It is a convienent-to-store arbitrary data in a persistent mechanism. In fact, it's rather like PHP ' s $_session array.

There is, however, one difference. $_session is the unique to a user (reused) across pages. With only one window to your website, the preform the same function. But if a user have multiple tabs or windows, $_session can change in between what would otherwise is the successive page Lo Ads.

The ViewState has a functions:

Storing properties for controls and forms, storing arbitrary data

The viewstate is responsible for ensuring a red label was still red (and doesn ' t default back to black) between page loads. Controls and forms manage this transparently from the developer (excluding a Non-obtrusive ViewState property on controls ). There is also a viewstate on the Page object. It would act like a dictionary, allowing-to-save arbitrary data to it.

The viewstate is a magical thing, and it achieves that through indirection. It's what separates a browser form submission from a user actually preforming an action. Prado and Fortitude both duplicate this functionality in PHP.

For a full example, take a look at Fortitude Form ' s code. But for today's purposes, I just wanted to demonstrate what to create a simple viewstate in PHP.

!--? phpif (array_key_exists ("ViewState", $_post)) {$viewstate = Unserialize (base64 _decode ($_post["viewstate")); $viewstate--->count++;} else {$viewstate = new Stdobject; $viewstate->count = 0;}? >page-load count:!--? = $viewstate--->count;? 

It preforms very similarily to $_session. Although I used an object, the it works just as well with an array. But it accomplishes a separate the scope for each page. Frequently in PHP, pagination results is placed in $_session, and that's means only one set can is used at a time without B Utchering the rest. In a page scope, any manipulations can is done at would. And that exposes the real difference between the two:global things, like login operation or options, should is set in $_s Ession. Local, page-level or temporary things should is set in the page ' s viewstate. Opening or three or even one hundred twenty copies of that script would maintain that many instances of $viewstate Count. $_session maintains only one.

Note that the security problems the Extremeexperts article mentions is just as true with PHP as ASP. A manipulative user could set ViewState to a custom crafted value and disrupt the applications expectations. But that just means judicious amounts of validation is required before consuming viewstate on postbacks. Both ASP. NET and PHP ' s viewstate can be made secure.

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