Understanding advance page template preprocessing

The main role of the page preprocessor is to set up custom variables to be rendered through the template (.tpl.php) files. Mostly the page preprocessing is used to handle theme template suggestions. This means that based on some custom logic we can suggest any page--*.tpl.php file instead of generic page.tpl.php but this is not the limit, most advance developers use these preprocessors to do heavy calculation of their logic and then pass the results to the page.tpl.php in form of some custom variable, this avenue has endless possiblities.

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