Python code doesn't typically use the get and set methods so common in PHP. Normally, when writing PHP code, you carefully protect your instance variables by making them private, so callers can only interact with them via getter and setter methods. [...] Python's solution to this problem is more readable, it has a construct called a "property".

He compares two blocks of code that do the same thing - set properties on the object with the PHP side doing a bit more error checking (seemingly) than the Python side. They both apply a title property to a book object.

Constructors are often used to shortcut dependency injection and parameter passing on instantiation. This is a valid practice and often leads to shorter code. [...] Instead of creating a new instance of "Money" and calling three setter, everything can be done compactly in the constructor. [...] So for the money object this works pretty well. The code is easy to read, but wait, the first argument can be grasped easily, the second too, but the third? It is not too obvious that it is a divisor is passed.

He compares three different ways to get the data into the class - the already-mentioned parameters in the constructor, passing an array into the constructor and using full getters/setters to push the data into the right places (with fluent interfaces even!).

This is a thought I first shared at CakeFest Orlando this year, but could not explain properly at the time.

He illustrates with an example of a protected "balance" variable in a BankAccount class. Sure, it's marked as private but less skilled programmers might not use it that way. He recommends a method without the getters/setters to help make the usage of the variable a bit simpler. He also suggests that using protected/private scoping helps to promote "crappy code" - using them to provide a sort of protection for code that you either don't want getting used or hiding it away so the API can't get at it.

Of course, when it comes to specifying how visible a certain class property or method will be, you know that PHP 5 permits you to work with three distinct levels of access, called "public," "protected," and "private" respectively. [...] As you may have noticed, however, I've not taught you how to define private methods yet, which is something that can definitely be very useful if you want to restrict the access to your classes from the outside more severely.

The tutorial shows the creation of a class with private properties and then expands it to include a private method. Then they call it from an object, an example of the error PHP kicks back is there too. He also includes the concept of a "getter" to call the private function from a public one.

"Do not use getters and setters" looks like a hastily advise, but its meaning is very important and it is "do not break encapsulation", which moves us to the question what the encapsulation is.

He notes that encapsulation is, in essence, hiding parts of the code away so that the user/other coders only see a little bit of the magic that happens. He argues that getters and setters are a valid part of the encapsulation process and that designing a good, easy to use system almost requires them.

Today most of the popular programming languages support objects, limiting scope, modularity, passing by value, and sophisticated built-in types. There should be no reason to deliberately expose an object's data to the rest of the code because the language can enforce encapsulation and data hiding.

While not specific to PHP, the post does recommend against them because of one simple reason common to all languages that make them possible - they "break the encapsulation OOP offers". For them, they're like a cheat to get around bad coding practices and are not needed to make a successful application work.

The usage of interceptors (__get()/__set()/__isset()/__call()) makes your API a lot more readable and comfortable, while maintaining the purpose behind getters and setters: Checking the correctness of values assigned to a property and wrapping around retrieval mechanisms for a property. I personally call the way of maintaining value-correctness for properties through interceptors virtual properties, which fits quite nice I think.

Tobias gives an example of what he means by these "virtual properties" with an illustration from something widely used on the eZ Components libraries - comparing one method of setting text to an object to another (just setting versus the wrappers).

Some times there are some ancillary methods to deal with unsetting, checking for existence, setting via an array, or dealing with references in PHP 4. They can really clutter up the definition of a class. That's not good.

[...] I think the idea is to make the class extensible. But PHP is really ok with just setting new properties on a class. So why not just do this?

He argues that getters and setters in a class are less useful than just setting the property yourself. Using the property name as part of the interface, though (like getting the $obj->foo value with $obj->getFoo) is stil clean enough to be useful.