In software engineering we try to discover and eliminate bugs as soon as possible. One of most important heuristics here is validation of input/output on functions and methods. If you are going with TypeScript or Flow, you are fine. But if not? Then we have to manually validate at least input (arguments). But what would be the best way doing it?
As developers we spend a lot of our time on debugging and particularly on spotting the source of a problem. DevTools guides us though the call stack, but the tracing process can be still pretty time consuming, especially on a cascade of asynchronous calls. The remedy here is early problem reporting.
You know, when coupling is not loose, components depend too much on each other. It makes your entire architecture fragile and immobile. You can check how loose the coupling is by making a unit test for a component. If you have no problem substituting dependencies by e.g. mock objects then everything is ok. Let take a model class. It depends on DB connection, here Lib_Db_Adapter_Interface instance. We cannot just create DB adapter instance within model constructor, because it depends on configuration data which don’t belong to the model. We can pass to the model constructor a settings array with DB configuration data.
However fondly you treat your application, errors happen and they happen often when it is being developed. That’s obvious you want to get all the tracing information during the development stage and something like ‘Application Error’ page if the error occurs on the production.
Everybody knows error handler can be set in PHP through set_error_handler. The same about exceptions for which set_exception_handler is used. But it really works only for user-defined errors and uncaught exceptions. It doesn’t affect any of fatal error for instance. Well, PHP has such stuff as register_shutdown_function to deal with them. We can create ErrorHandler class and subscribe the handlers in the beginning of the script