Many times when carrying out a task code needs to be factored across multiple logic sets. Using an OO approach makes it very simple to hide these parts from the rest of the application.
A single entry method can be used within public scope, having all the other support-oriented methods limited to the classes scope.
This approach supports very poor coding practices and non-reasonable segments of logic. For that of many reasons reason, I prefer the DI approach and rarely, if ever resort to functions, unless native to the language of-course. The question is: am I right? Functions have a mechanism to do this.
To a degree. Here… Encapsulation - related methods and data are bound together. Inheritance - Code is reused by having child classes inherit methods and members from parents. Polymorphism - Code can be changed, provided the functions are granular enough, by creating child methods that override their parent methods. Note: In a class, variables are called properties and functions are called methods!
Classes are nothing without objects! We can create multiple objects from a class. Each object has all the properties and methods defined in the class, but they will have different property values. You can use the instanceof keyword to check if an object belongs to a specific class:.
We just launched W3Schools videos. Get certified by completing a course today! A property might be:. With each, I have defined a valid type, so that we always know what we'll receive from the property, as well as what values will be accepted. Property type hints were only added in the PHP 7. Previous versions did not allow them. Instead, you used the var keyword currently deprecated , or a visibility operator.
To keep the examples simpler, we are demonstrating declarations with type only. Properties can also be declared static, meaning the value is the same between instances, or given visibility, which defines where and when they may be accessed. Those concepts are beyond the scope of this article, however. We can provide behavior by defining methods on the class. A method is a function scoped to the class instance.
Just like normal functions, methods can accept arguments, and will have an associated return value. Generally speaking, you will want to write these such that they do not have side effects; that means they usually should not change state in the instance, or produce output e. The primary difference with a function is that it has access to the instance properties, which means it can use them either in its behavior, or to produce behavior if the properties are themselves other object instances or functions.
Let's write a method that will compare the number of wheels in the instance against another instance; the idea will be that we could use the method to help sort WheeledVehicle instances by the number of wheels they have. For our purposes, we'll consider the current instance the "left" side of an operation. The public keyword is used to define visibility of the method, which is essentially who can call it, and where it may be called.
Methods have public visibility by default, but it is best to define the visibility explicitly. We will cover visibility in a later article, as it's a more advanced topic. Methods can have as much or as little logic as you need in them in order to create the behavior required. The important thing to remember is that they are just PHP functions that have access to the current instance, which means they can access properties and call their own methods.
It would be nice not to have to set all the properties of a car. What if we could define those and still have the concept of a "wheeled vehicle"?
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