Web Design & Development - Session 9
This document provides an overview of various object-oriented programming concepts in PHP including constructors, static methods, constants, encapsulation, access levels, inheritance, interfaces, abstract classes, and traits. It defines each concept and provides examples. Constructors initialize object properties when an object is created. Static methods are called on a class rather than an object. Constants are declared in uppercase. Encapsulation controls property and method visibility. Access levels include private, protected, and public. Inheritance allows a subclass to inherit from a parent class. Interfaces define methods a class must implement without defining how. Abstract classes serve as templates for child classes. Traits allow classes to reuse methods from multiple sources to prevent code duplication.
Web Design & Development - Session 9
- 1. Web Design and Development By: Shahrzad Peyman Session 9 December-2017 [email protected] 1
- 2. 2 Today’s Presentation • self • Inheritance • Access Level • Interface • Abstract • Trait
- 3. Constructor 3 When creating a new object, you can pass a list of arguments to the class being called. These are passed to a special method within the class, called the constructor, which initializes various properties.
- 4. Static Method 4 You can also define a method as static, which means that it is called on a class, not on an object. A static method has no access to any object properties and is created and accessed as in below example:
- 5. Declaring Constants 5 You can define constants inside classes. The generally accepted practice is to use uppercase letters to make them stand out.
- 6. Encapsulation 6 In basic terms, it’s the way we define the visibility of our properties and methods. • When you’re creating classes, you have to ask yourself what properties and methods can be accessed outside of the class.
- 7. Access Level 7 Specifier Class SubClass all Private * Protected * * Public * * *
- 8. Inheritance • In object-oriented programming, inheritance is when a class is based on another class, using the same implementation or specifying a new implementation to maintain the same behavior. • Such an inherited class is called a subclass of its parent class or super class. 8
- 10. Inheritance 10
- 11. 11 Interface An interface is an outline of what a particular object can do. You will often hear that an interface is a contract. This is true in as much as an interface defines the public methods that a class must implement. Object interfaces allow you to create code which specifies which methods a class must implement, without having to define how these methods are handled.
- 12. Interface 12
- 13. Abstract 13 An abstract class is a special type of class that can't be instantiated — in other words, you can't create objects from it. Instead, you create child classes from the abstract class, and create objects from those child classes instead. An abstract class is designed to be used as a template for creating classes. An abstract class will have abstract methods which are defined by the abstract keyword, these methods are like the methods defined in the interface classes.
- 14. 14 Abstract
- 15. Interface vs Abstract Interface Abstract The Code • abstract methods • constants • abstract methods • constants • concrete methods • concrete variables Access Modifiers • public • public • private • protected Number of Parents Class can impelement more than one interface Class can inherit only from one abstract class 15
- 16. Trait 16 One of the problems of PHP as a programming language is the fact that you can only have single inheritance. This means a class can only inherit from one other class. However, a lot of the time it would be beneficial to inherit from multiple classes. For example, it might be desirable to inherit methods from a couple of different classes in order to prevent code duplication.
- 17. 17 Trait A Trait is simply a group of methods that you want include within another class.