On a site with a reasonable amount of traffic , would it matter if the application/business logic is written as stored procedures ,triggers and views , instead of inside the PHP code itself?
What would be the best way to go keeping scalability in mind.
I can't provide you statistics, but unless you plan to change PHP for another language in the future, i can say keeping the business logic in PHP is more "scalability friendly".
Its always easier and cheaper to solve web server load problems than having them in the database. Your database will always need to be lighting quick and just throwing mirrors at it won't solve the problem. The more database slaves you have, the more writes you have to do.