PHP OOPS interview questions and answers (2023)

An object-oriented programming system and OOPs It is a programming language model organized around objects. Objects are instances of classes used to interact with each other. An application can be of any type, such as a web-based application, a windows-based application, etc. Object-oriented programming is all about the objects and the class. OOPS is short for object-oriented programming system, in which programs are viewed as a collection of states.

Concepts of OOPS:

1. Abstraction
2. Encapsulation
3. Inheritance
4. Polymorphism

• Inheritance
• Data Encapsulation
• Extensible data types and classes
• Support for complex data types
• Aggregation
• Association

A class is simply a type of object. It is the plan or template that describes the details of an object.

An object is an instance of a class, It has its own behavior, state behavior, and connections.

The encapsulation is part of an object and describes all data. Hidden data is restricted to members of this class. Classes are public, private, protected, internal, and internally protected.

Polymorphism is nothing more than assigning behavior or value in a subclass to something that has already been declared in the main class. Polymorphism simply takes on more than one form.

Inheritance is a concept whereby one class assigns the formation and behavior defined in another class. If the inheritance applies to one class, this is referred to as single inheritance; if it depends on several classes, this is referred to as multiple inheritance.

Manipulators are purposes that can be used in combination with the insert (<<) and extract (>>) operators on an object. Examples are endl and setw.

• Interfaces don’t include business logic.
• You must extend the interface to use.
• A class can be instantiated by making its objects. An interface is not be instantiated as the methods declared inside an interface are abstract and do not perform any action.
• You can’t create an object of the interface.
• A class is declared using a keyword ‘class’. An interface is created using a keyword ‘interface’.
• The members of a class can have access specifiers like public, private, protected. The members of an interface are public as they have to be accessed by the classes implementing them.
• The methods inside a class are assigned to act on the fields listed in the class. As interface requires in the declaration of fields, the processes inside an interface are purely abstract.

• Interfaces are assigned using the interface keyword.
• All methods are declared in an interface that must be public. Classes defined as Interface is not be instantiated(create object).
• You can inherit the number of interface class at the time of extending and number of abstract class separated by a (,)comma.
• All methods must be implemented within a child class, failure to do so will result in a fatal error.
• To extend the interface class, the implements operator is used.
• The extends operator is used.
• A number of the parameter must match.

It is a dynamically created method/resource and performed by magic methods. Overloading method/resources are invoked when interacting with properties or methods that have not been published or are not visible in the current field, Means we you are calling a function that does not exist.

View more on overloading here with example.

Function overloading is a normal function, but it can perform several tasks. It allows creating several methods with the same name which differ from others by the type of both input and output of the function.

A function where several operators are applied and based on the arguments is called Operator Overloading. Operator -,* can be used to pass by the function, and it has its own precedence to execute.

Binding is the name of the class. Static Binding is binding in that name may be related to the class and it’s also referred to as as early binding. Dynamic Binding is binding in call may be related to the class in the course of execution time, and it’s far referred to as as Late Binding also.

Zero Instances will be made for an abstract class. In other words, you can’t create an instance of an Abstract Class.

The operator keyword is used for overloading.

Abstraction is a key feature of OOPS and explains the necessary details of an object to the client. Displays only the necessary details for an object, not an object’s internal constructors. If you want to turn on the TV, it is not essential to know the internal circuitry required to turn on the TV. Everything needed to turn on the TV is described by an abstract class.

Access modifiers describe the scope of the method and variables that can be accessed from other different objects or classes. Five types of access modifiers and they are as below:

• Private
• Public
• Protected
• Friend
• Protected Friend

The Scope Resolution Operator is a double colon (::) that allows a way to static, constant, and overridden properties or methods of a class.

• Access the constant.
• Access the methods of a parent class.
• Access the overridden properties of the parent class.

• Default Constructor:- With no parameters.
• Parametric Constructor:- Create a new instance of a class and also passing arguments simultaneously with Parameters.
• Copy Constructor:-Which forms a new object as a copy of an existing object.

• Traits are a circuitry for code reuse in single inheritance.
• A Trait is similar to a class, but only intended to group functionality in a fine-grained and consistent way.
• It is impossible to instantiate a Trait but in addition to common inheritance. It is assigned to reduce some limitations of single inheritance to reuse sets of methods freely in several independent classes living in several class hierarchy.

• Code Reusability: Used to achieve through inheritance and traits.
• Modularity: Used to achieve by breaking large code into small modules, Modularity reduces complexity.
• Maintainability: Used to maintain code that follows Object-Oriented Programming Concepts.
• Testability: it is easy to test.
• Security: Used to achieve by Encapsulation
• Flexibility: We can make by polymorphism.
• Testability: it is easy to test.