Object-Oriented PHP shows developers how to take advantage of the new object -oriented features of PHP. Working from concrete examples, the book begins. As the demand for object oriented PHP programmers grows day by day, it is tutorials website that teaches Object Oriented PHP on which this eBook is based. With the release of PHP 7, Object-Orientation has matured significantly in PHP. This book Learn more about Leanpub's ebook formats and where to read them .
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The concept of object-oriented programming may seem daunting. We put together a comprehensive ebook to help you get started with. Preamble. The hardest thing to learn (and teach btw,) in object oriented PHP is the basics. Like Java and C#, php finally has a complete OOP infrastructure. Arm yourself with what you need to level up as a PHP developer. This ebook goes in-depth on Objected-Oriented PHP (OOP) to help make.
This version-neutral book is a gentle introduction to object-oriented programming OOP that won't overburden you with complex theory.
It teaches you the essential basics of OOP that you'll need to know before moving onto a more advanced level, and includes a series of prepackaged scripts that you can incorporate into your existing sites with the minimum of effort. It shows how object-oriented programming can be used to create reusable and portable code by walking you through a series of simple projects. The projects feature the sorts of things developers run up against every day, and include a validator for filtering user input, a simple Date class that avoids the need to remember all the esoteric format codes in PHP, and an XML generator.
As a professional writer, he has been involved in electronic media for more than 30 years, first with BBC radio and television and more recently with the Internet. His clear writing style is valued not only in the English-speaking world; several of his books have been translated into Spanish and Polish.
What started as a mild interest in computing was transformed almost overnight into a passion, when David was posted to Japan in as BBC correspondent in Tokyo. With no corporate IT department just down the hallway, he was forced to learn how to fix everything himself.
When not tinkering with the innards of his computer, he was reporting for BBC television and radio on the rise and collapse of the Japanese bubble economy. Since leaving the BBC to work independently, he has built up an online bilingual database of economic and political analysis for Japanese clients of an international consultancy.
We have two variables in the class definition. The private keyword is an access modifier. It is a form of encapsulation.
The private keyword is the most restrictive modifier. It allows only the object in question to access the variable. No descendants, no other objects. More about this topic later. In the constructor, we initiate the two data members.
We create a Friend object with two arguments. Then we call the getInfo method of the object. PHP enables to create class constants. These constants do not belong to a concrete object. They belong to the class. By convention, constants are written in uppercase letters.
Class constants are accessed from within methods using the self keyword followed by two colons. We print the PI constant to the console.
In the first case, we get the constant value by referring to the class name, followed by two colons and a constant name. Note that no object was needed to get the class constant. In the second case, we use the object method. The instanceof keyword is used to determine whether a PHP variable is an instantiated object of a certain class. In the above script, we have three classes: Cat , Dog , and Bird. We traverse the array and print the class for each array value.
We will demonstrate this in the following example. The inheritance is a way to form new classes using classes that have already been defined. The newly formed classes are called derived classes, the classes that we derive from are called base classes. Important benefits of inheritance are code reuse and reduction of complexity of a program.
The derived classes descendants override or extend the functionality of base classes ancestors. In this PHP script, we have two classes: The Derived class inherits from the Base class.
PHP Object Oriented Programming (OOPs) concept Tutorial with Example
In the constructor of the Derived class, we call the parent constructor. The constructors of the parent classes must be called explicitly. We have used several new concepts here. In the code example, we have three classes: Being , Animal , and Cat. The Animal class inherits from the Being class. The Cat class inherits from the Animal class. Classes inherit methods and data members that are not declared as private.
The Being class is declared to be abstract. The abstract keyword prohibits instantiation of classes. It does not make much sense to create an instance of the class Being. Such members can be accessed only by the classes that define them and by their descendants. The Animal class is also declared to be abstract.
It inherits from class Being. For this, we use the extends keyword. The Animal is a descendant.
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It inherits methods and variables of the base Being class. It inherits from the Animal class and indirectly from the Being class too. It is not declared abstract, which means that we can instantiate it. We create a new Cat: Cici, 4 years old. Then we call functions on the cici object. Note the usage of methods that were not created in the Cat class, but rather inherited from the parent classes. PHP 5 introduced abstract classes and methods. Abstract classes cannot be instantiated.
If a class contains at least one abstract method, it must be declared abstract too. Abstract methods cannot be implemented, they merely declare the methods' signatures.
When we inherit from an abstract class, all abstract methods must be implemented by the derived class. Furthermore, these methods must be declared with the same or with a less restricted visibility. Unlike interfaces , abstract classes may have methods with full implementation and may also have defined member fields. So abstract classes may provide a partial implementation. Programmers often put some common functionality into abstract classes. And these abstract classes are later subclassed to provide more specific implementation.
For example, the Qt graphics library has a QAbstractButton , which is the abstract base class of button widgets, providing functionality common to buttons. Formally put, abstract classes are used to enforce a protocol.
A protocol is a set of operations which all implementing objects must support. In our PHP script, we have an abstract base Drawing class. The class defines two member fields, defines one method and declares one method. One of the methods is abstract, the other one is fully implemented. The Drawing class is abstract because we cannot draw it. We can draw a circle, a dot, or a square.
The Drawing class has some common functionality to the objects that we can draw. A Circle is a subclass of the Drawing class. It must implement the abstract area method. A remote control is an interface between the viewer and the TV. It is an interface to this electronic device.
Diplomatic protocol guides all activities in the diplomatic field. Rules of the road are rules that motorists, cyclists, and pedestrians must follow.
Interfaces in programming are analoguos to the previous examples. Objects interact with the outside world with the methods they expose. The actual implementation is not important to the programmer, or it also might be secret.
A company might sell a library and it does not want to disclose the actual implementation. A programmer might call a maximize method on a window of a GUI toolkit, but knows nothing about how this method is implemented.
From this point of view, interfaces are methods through which objects interact with the outside world, without exposing too much about their inner workings.
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From the second point of view, interfaces are contracts. If agreed upon, they must be followed. They are used to design an architecture of an application, and they help organize the code.
Interfaces are fully abstract types. They are declared using the interface keyword. Interfaces can only have method signatures and constants. All method signatures declared in an interface must be public. They cannot have fully implemented methods, nor member fields.
A PHP class may implement any number of interfaces. An interface can also extend any number of interfaces. A class that implements an interface must implement all method signatures of an interface.
Interfaces are used to simulate multiple inheritance. A PHP class can extend only one class. A PHP class can implement multiple interfaces. Multiple inheritance using the interfaces is not about inheriting methods and variables. It is about inheriting ideas or contracts, which are described by the interfaces. There is one important distinction between interfaces and abstract classes. Abstract classes provide partial implementation for classes that are related in the inheritance hierarchy.
Interfaces on the other hand can be implemented by classes that are not related to each other.We echo the object. Programmers often put some common functionality into abstract classes. Classes and objects 2 Practice: The Animal class is also declared to be abstract. To find out more info, we call the getMessage method on the exception object.