Object Oriented Programming (OOPs) Concepts in PHP

Class - 

• Class is the template which contains class members. class members are properties and methods.

• Property - Variable declared within the class.
• Method - Function declared within the class.

Object - 

• An object is the memory location of the class variables. We can access the class variables with the support of object.

New - 

• By using this keyword we can allocate space in the new memory locations to load class content.

Constructor - 

• The constructor is one the type of method which is having class name same as method name. By default, every class contains a default constructor used to load class constraints.
• In PHP we can use constructor in two ways -
• Using constructor keyword (default constructor) - __constructor().
• Using class name - className().

Destructor - 

• Destructor is the special type of method, which can be executed at the time of destroying object of class. By using __destructor() we can create destructor.
• In PHP, the class objects will get destroyed when execution of the script is completed. We can also destroy class object between script execution using the unset function.

Inheritance -

• When a class is defined by inheriting the existing function of a parent class then it is called inheritance. Here child class will inherit all or a few member functions and variables of a parent class.

Parent class -

• A class that is inherited from another class. This is also called a base class or superclass.

Child Class − 

• A class that inherits from another class. This is also called a subclass or derived class.

Polymorphism - 

This is an object-oriented concept where the same function can be used for different purposes. For example, the function name will remain the same but it takes a different number of arguments and can do different tasks.

Data Abstraction - 

• Any representation of data in which the implementation details are hidden (abstracted).

Encapsulation - 

• This refers to a concept where we encapsulate all the data and member functions together to form an object.

Constants -

• A constant is somewhat like a variable, in that it holds a value, but is really more like a function because a constant is immutable. Once you declare a constant, it does not change.

Abstract Classes - 

• An abstract class is one that cannot be instantiated, only inherited. You declare an abstract class with the keyword abstract.

Static Keyword - 

• Declaring class members or methods as static makes them accessible without needing an instantiation of the class. A member declared as static can not be accessed with an instantiated class object (though a static method can).

Final Keyword - 

• PHP 5 introduces the final keyword, which prevents child classes from overriding a method by prefixing the definition with final. If the class itself is being defined final then it cannot be extended.