Web application with a single entry point
Published on 2015-01-01.
I was reading a bit about so-called RESTful applications and I stumbled upon an article called "Writing modern day PHP applications". The author of the article states that he sometimes comes across third party code that he believes exhibit features that "were customary in the 90's". One such feature is applications not having a single point of entry. The author states:
Back in the days where the rewrite module was an uncommon luxury creating multiple .php files in the webroot was the standard.
Like so many others the author has completely misunderstood the point of the architecture he is working with!
I don't know if it's because of the way things work today, where people have become used to simply "point-and-click" or throw out (when something isn't working), or if it's a lack of thoroughness in studying the underlying technology, but something is horribly wrong with how most things are being developed - especially web applications and even more so front-end development.
It's like something becomes modern because some popular person says it is the right thing to do, or because someone manages to seduce the masses and everyone follows suit.
Back "in the days" getting things to work was often difficult. It took a lot work and a lot of patience. But there was a benefit, it provided a thorough understanding of the underlying technology and how to get the best results using it.
I cannot say it any better than Rasmus Lerdorf (the inventor of PHP):
Just make sure you avoid the temptation of creating a single monolithic controller. A web application by its very nature is a series of small discrete requests. If you send all of your requests through a single controller on a single machine you have just defeated this very important architecture. Discreteness gives you scalability and modularity. You can break large problems up into a series of very small and modular solutions and you can deploy these across as many servers as you like.
What Rasmus Lerdorf is describing is in reality based upon the Unix philosophy of "Doing One Thing and Doing It Well".
Even if you're working on a web application that's never going to need to scale up to multiple servers, you're only adding layers of complexity where the application can break (which is something we see every day), and simulating yet another single entry point makes the application noticeable slower. That is one reason why most frameworks are notoriously inefficient and horrible. The more you abstract away from the core, the less efficient it becomes.
Some people state that it is all about being DRY (Don't Repeat Yourself). That if you have multiple php files (or whatever programming language you use for web development) handling requests you will have duplicated code.
Having multiple files handling requests has nothing to do with code duplication, it all depends on how the application is designed, and how the separate structures are bundled together, but no application is completely free from some code duplication, even if only minor duplication.
Other people talk about encouraged separation of "business logic" and "layout logic", unified access to the objects for database queries, service calls, etc. But such arguments has nothing to do with a single entry point in the web application what so ever, and such arguments really exists as the result of a lack of experience with scalability. Separation of logic can be handled in numerous ways without using a single entry point.
Another author on another article called "Why does PHP suck?" states:
PHP's "drop 'n run" concept also has a lot of shortcomings. Sure, it's nice to just drop a script in a folder on the web server and have it run. That is, until you realize that now you have an infinite number of entry points into your application, even though you just need one. If you take a look at the big boys like WordPress, you'll see that all requests are being redirected to a single entry point and then dispatched further - which is how it should be.
This is again an example of a lack of knowledge of the underlying technology. The webserver IS the single entry point, not the PHP application.
Looking at how the so-called "big boys like WordPress" are doing things, are really bad advice. What "big boys" are doing is not a guideline for correctness.
Re-writing requests only to have the web application interpret those requests, using yet another layer of complexity, seriously effects the efficiency of that application even on modern hardware, unless of course you're running a simple website with no real traffic. It's just plain stupid to add all those layers of complexity. Have you every profiled Wordpress? It's horrible slow.
Religiously following the "dos and don'ts" of the "web sheep packs" will without a doubt make you embark on a wild goose chase, trying to perfect something that has become inherently imperfect - or actually just plain and simple wrong.
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