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Best 30 PHP OOPS Interview Questions and Answers

If you’re new to the field of PHP OOPS programming, preparing for a job interview can be difficult. You may have the information and skills required to perform well, but the stress of being asked difficult questions can make you nervous. To help you prepare, we’ve developed a list of commonly asked PHP interview questions for freshers that will give you an idea of what to expect.


Prep yourself beyond the qualifying mark with the best sample question answers and interview tips from our top PHP developers. These questions cover a wide range of PHP concepts, from fundamentals to advanced issues. So let’s get started and prepare for your next PHP interview!

What is a PHP Object-Oriented Programming-Based Career?

PHP is an acronym for PHP hypertext preprocessor widely used as an open-source, object-oriented programming language.

It is specially designed for creating dynamic websites and mobile APIs. It is the best career to enter the job market at the current time. Usually, any PHP is qualified through interviews rather than merit. There are various advantages of object-oriented programming over procedural programming:

  • First, OOP is a more efficient and straightforward method of programming. The programmes have a clear structure, thanks to OOP.
  • Second, OOP helps keep PHP code DRY (Don’t Repeat Yourself), making it easier to maintain, alter, and debug.
  • Third, OOP allows developers to design whole reusable applications with less code and less time.

Let’s pretend we have a Fruit class. Fruit can have characteristics such as name, colour, weight, and so on. So $name, $colour, and $weight are variables that can be used to store the values of these characteristics.

When the individual objects (apple, banana, etc.) are formed, they inherit all of the class’s attributes and behaviours, but the values for the properties will be different for each object. Let’s pretend we have a Fruit class. A fruit can have characteristics such as name, colour, weight, and so on. $name, $colour, and $weight are variables that can be used to store the values of these characteristics.

When the individual objects (apple, banana, etc.) are formed, they inherit all of the class’s attributes and behaviours, but the values for the properties will be different for each object.

While preparing for PHP oops interview questions they can be subdivided into three sections.

  • Beginner label PHP oops interview questions
  • Intermediate label PHP oops interview questions
  • Advanced level PHP oops interview questions

Without doing any for the delay let’s jump in.

Top 30 Basic PHP Developer Interview Questions

To help you prepare for your upcoming PHP interview, we’ve provided a list of 30+ PHP interview questions, especially for freshers. These questions cover a wide range of topics, including basic syntax and more complex concepts like database connectivity and security. By practising these questions, you will obtain the confidence and knowledge required to ace your PHP interview and begin your career in web development.

1. What is oops and what are its basic concepts with their definitions? (High order thinking PHP oops interview questions)

Oops is an acronym form of object-oriented programming system where programs are treated as an object collection and each object is just an instance of a class. There are four kinds of concepts mentioned under Oops. They are-

  • Abstraction – is a concept in object-oriented programming that “shows” only the most important features while “hiding” the rest. The basic goal of abstraction is to keep users from having to deal with extraneous details. It is one of the most crucial OOP ideas.
  • Encapsulation – is a concept within the study of oops that is regarded as an attribute of an object. It contains all kinds of hidden data within it and this data can be restricted to the members of that class. Different types of levels found in encapsulation are Public, Protected, Private, internal, and protected internal.
  • Inheritance – is a concept under PHP object-oriented programming. This is where one class shares the structure and behaviour that is described by another class. This is again subdivided into two forms-
  • If the inheritance is in one class then it is known as a single inheritance
  • If the inheritance is depending upon multiple classes then it is known as multiple inheritances.
  • polymorphism – is described as assigning behaviour or value in a subclass to something already declared in the main class. In other simple words, polymorphism means taking more than one form.


2. What do you mean by a class and what is the difference between an object and a class? [Most frequently asked PHP oops interview questions]

A class is considered a representation of a particular type of object. It is a template that describes the details of that object. An abstract class cannot be instantiated. Abstract class does not facilitate creating an object, but these objects can be inherited. Only an abstract methodology helps in the creation of an abstract class.

The computer language only allows abstract methodology in creating abstract classes, while other languages consist of both non-abstract and abstract in their abstract class.

The object is a smaller subunit of the class. Objects hold the actual multiple information whereas classes don’t have any kind of information.

The definition of properties and functions are performed in a class and are used by the object. A class can be subdivided while an object cannot be. It is not possible to create an instance of an abstract class.

3. What is Encapsulation?

Encapsulation is the binding of data and procedures that manipulate them into a single unit so that the sensitive data is hidden from consumers.

It is implemented using the processes listed below:

  1. Data hiding: A language feature that limits access to members of an object. For example, in C++, there are private and protected members.
  2. Bundling data and methods together: Data and methods that operate on that data are combined. For example, the data members and the member methods that operate on them are combined into a single entity called a class.

Java

//simple demonstration of encapsulation

//It has a private data member and getter and setter methods. 
public class Student{ 

//private data members

  private String name;  

 private int rollNo;

//public getter method to access the name  

public String getName(){  

       return name;  
 }  

  //public getter method to access rollNo  

    public int getRollNo(){  

      return rollNo;  

    } 
//public setter method to set name  

    public void setName(String name){  

          this.name=name  
}

 //public setter method to set rollNo  

    public void setRollNo(int rollNo){ 

            this.rollNo=rollNo;  

    }  
}

4. What is Abstraction?

Abstraction, like data encapsulation, is critical in object-oriented programming. It involves showing only the necessary information and hiding any other unnecessary data from the user. Abstraction is implemented by classes and interfaces.

5. What are the different types of Polymorphism?

Polymorphism is divided into two types dependent on the time when the call to the object or function is completed. They are as follows.

  1. Compile Time Polymorphism
  2. Runtime Polymorphism

A) Compile-Time Polymorphism

Compile time polymorphism, also known as static polymorphism or early binding, is a sort of polymorphism in which the call is bound to the code at compile time. Compile-time polymorphism includes method overloading and operator overloading.

B) Runtime Polymorphism

Runtime polymorphism, also known as dynamic polymorphism or late binding, is a type of polymorphism in which the function’s actual implementation is determined during execution. Overriding methods is one example of this strategy.

6. The difference between final class and final method [Beginner level PHP OOPS interview questions]

The final keyword used in a method declaration represents that any subclass cannot override the said step. At the same time, a class declared as final cannot consist of any subclass.

These terms are advantageous in creating an immutable class such as a string class. No other entities such as properties can be declared as final except for classes and methods.

7. What do you mean by an object in PHP and what are the different kinds of PHP variables in object-oriented programming? [Most frequently asked PHP OOPS interview questions]

An object is an instance of a particular class that has its behaviour state and identity.

There are 8 data types in total within the study of PHP variables. They are as follows :

  • Integers– any kind of whole number without any decimal point. for example 5162
  • Double-these are the floating numbers that can consist of decimal points. for example 41.1
  • Boolean -these are the data types that have two possible values that are false or true.
  • NULL– it is a special data type that has only one value assigned to it.
  • Strings-these are the sequences of characters
  • Arrays– these data types are named and indexed collections of various values.
  • Object– these are the data types that are instances of programmer-defined classes that can package other values and functions specific to the class.
  • Resources– These are data types with special variables that can hold references to any external resources to PHP.

8. What is a constructor, manipulator and destructor? [Most frequently asked PHP OOPS interview questions]

A constructor is a methodology that is used to initialise the state of an object. It is initiated at the time of the creation of an object. The two basic rules for construction are

  • Constructor names should always be mentioned according to the same class name.
  • There should be no return type in a constructor.

Manipulator is described as functions used in conjunction with the insertion and extraction operator on the object.

A destructor is a methodology that automatically is called on when the object is made up of scope or destroyed. Destructor name should also be mentioned as the same class name but with a tilde symbol before its name.

9. Define the terms virtual function and friend function. [High-order thinking PHP OOPS interview questions]

A virtual function is described as a member function of a class. The functionality of the virtual function can be overridden from its derived class. The function is initiated by using a Keyword called virtual and it is given at the time of function declaration.

This function is declared when using a token in C ++. It can also be achieved in C++ and Python by using different function pointers to the function.

A friend function is a class that is allowed access to any public, private, or protected data provided that it is within the same class. If this function is defined beyond the class there, it cannot access such information.

A friend function is declared anywhere during the class declaration. Thus, the friend function is not affected by access control keywords such as private, public, or protected. 

10. What is considered a function overloading and operator overloading? [High-order thinking PHP OOPS interview questions]

Function overloading is a type of regular function that can carry out different kinds of tasks. This function allows the creation of several steps with the same name that differ from each other by the type of input and output of the function. A small example of this instant is

Void add(int& a, int&amp  b);

Void add(double& a,double& b, );

Void add(struct bob& a,struct bob& b, );

[This is an ideal way to answer this OOPS interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers.

The term operator overloading means a function where various operators are applied depending on the arguments. For example, an operator such as ‘-‘ and ‘*’ is used to pass through a function along with its presidents to execute.

11. What does the term ternary operator mean? [Beginners PHP OOPS interview questions]

It is an operator that takes three arguments. These arguments are of different data types depending on the function. It is also often termed a conditional operator.

12. What is the function of the finalize method? [Most frequently asked PHP OOPS interview questions]

The finalize method helps to clean up the resources that are not currently in use. It is protected and thus accessible only through the same class or a derived class.

13. Mention different kinds of arguments. [Beginner PHP OOPS interview questions]

A variable is used at the time of declaration of a function or a subroutine. The arguments follow the body of the function by matching the defined variable. An argument can be of two types namely-

  • Call by Value arguments
  • Call by Reference arguments

14. What do you mean by method overriding? Differentiate between overloading and overriding. [Most frequently asked PHP OOPS interview questions]

Method overriding allows a subclass to command the implementation of a method that can override the main class. The implementation thus given will override by the same method name, same variable, and same return type.

Overloading is a Static Binding that has the same method with different arguments. This may or may not return equal value within the same class on its own. Why overriding is a dynamic binding process with the same method names with the same arguments and return type associated with the class and its subclass.

[This is an ideal way to answer this PHP OOPS interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers]

15. What do you mean by exception handling? [Beginner PHP OOPS interview questions]

An exception is a situation that arises during the execution of any program. These are of two types-runtime exception and error exceptions. These exceptions are handled through 3 exception handling mechanisms, catch and throw keywords.

16. What do you mean by tokens? [Beginner PHP OOPS interview questions]

A token is usually recognized through a compiler where it can’t be broken down to component elements. A few examples of tokens are keyword identifiers, string literals and operators.

Tokens also consist of punctuation characters such as brackets, braces, commas and parentheses.

17. What do you mean by access modifiers? [Beginner PHP OOPS interview questions]

Access modifiers are the feature that is used to determine the scope of the method or variable that is accessed from various objects or classes. There are mainly five kinds of access modifiers namely-

  • private
  • Protected
  • public
  • friend
  • Protected friend.

18 What is the function of a pure virtual function? give an example. [High-order thinking PHP OOPS interview questions]

A pure virtual function is an undefined function that can be overridden within the derived class. Any virtual function can be declared as pure by using the operator sign of =0.

For example

1virtual void function () // virtual. Not pure

2

3 virtual Void function () = 0 // pure virtual

[This is an ideal way to answer this OOPS interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers]

19. State all the operators which cannot be overloaded. [Beginner PHP OOPS interview questions]

Three types of operators cannot be overloaded. They are as follows

  • Scope resolution
  • members selection
  • member selection through a pointer to a function

20. Give examples of constants in PHP along with their purpose. [Most frequently asked PHP OOPS interview questions]

  • LINE– this constant represents the current line number of a file
  • FILE– this constant represents the full path and file name of a particular file. In case it is used within and includes the name of the included file is returned
  • FUNCTION – this is used to represent the name of the function
  • CLASS– this is used to represent the class name as it was assigned
  • METHOD -it is used to represent the class method name

Advanced Level PHP Developer Interview Questions.

21. What is the meaning of NULL? [High-order thinking PHP OOPS interview questions]

A special type of data that can have only a single assigned value is known as NULL. In the case of variable data type null, it has no value assigned to it. It can be represented as follows-

1 $var = NULL;

If the special constant NULL is capitalized then the case is considered insensitive. You can also assign it as

1 $var = null;

Following are the properties of the variable assigned through the NULL value

  • It determines FALSE in a Boolean context
  • While testing with the IsSet() function, it returns FALSE.

22. State the differences between PHP constant and variable in object-oriented programming. [intermediate PHP OOPS interview questions]

Constant

  • It is not necessary to mention the Dollar sign before the constant
  • They can be defined only by using the define() function.
  • They may be accessed and assigned anywhere without any regard to variable scoping.
  • Constant can never be redefined or undefined

Variables

  • The Dollar sign must be mentioned while writing a variable
  • The variable has to be defined by a simple assignment
  • In PHP by default, functions can only create and use variables within their scope.
  • For each path, the variable can be redefined individually.

[This is an ideal way to answer this OOPS interview question in particular. However, you can answer in your own words after understanding the core matter from the given answers

23. When should you use=== in place of ==?[High-order thinking PHP developer interview questions]

If the developer wants to check for a certain type, for example, integer or Boolean, the === will perform exactly the expected task from a strong type language. Whereas == word converts a type of data temporarily while trying to match with both operand types.

The Identity operator represented by === performs better because of not having to deal with any type of conversion. In case of inspections of variables for true/ false, the developers should avoid using == as this will take into account 0/1 and other similar kinds of representations.

24. What are the PSR standards you usually follow and why should you follow them? [Most frequently asked PHP OOPS interview questions]

PSR should be followed because coding standards always tend to vary between developers and companies. Therefore, issues can arise while reviewing another developer’s code and finding a code structure that is very different from your own.

In such cases, the PSR standard helps to determine the expectation of how the code should look like. This is done by eradicating all kinds of confusion and in some special cases, Syntax error too.

25. What are the three scope levels available in PHP? Define them. [Most frequently asked PHP interview questions]

The 3 scope levels are as follows-

  • Private- this quote is only visible to its class
  • Public- this scope is visible to any kind of code that is accessing that particular class
  • This is only visible to parent classes and the classes that are extended from the current class.

26. How can one prevent the following warning-” warning; cannot modify header information headers already sent”? Also, mention when this occurs.

In this answer, the candidate appearing in the PHP Oops interview questions should not output anything into the browser using a course that modifies HTTP headers.

Once the interviewer causes echo or any other code that clears the buffer then the developer can no longer set cookies or headers into it. This is also true regarding error messages full stop in the case where an error happens before the header command is used then the directive display-error is set.

27. What types of rules are considered to determine the “truth” of any value that is not already because of Boolean type? [Most frequently asked PHP OOPS interview questions]

Here is the list of rules that are used to determine the truth of any value that is not already of Boolean type

  • If the value is in the form of a number then it is false in the case where it is exactly equal to zero and true otherwise.
  • In the case where the value is a string then it is considered false if the string is empty.
  • If the value is in the form of an Array then it is false if it contains no other values and it is considered true otherwise. In the case of objects containing a value means having a member variable that has already been assigned a certain value.
  • Values for any NULL function are always false.
  • Every valid resource provided is always true
  • Never use double as Boolean

28. Mention the characteristics and respective rules necessary for naming a PHP variable.

Important characteristics of PHP variables are as follows

  • All variables in PHP are denoted after writing a Dollar sign
  • The value of the variable is assigned according to its most recent assignment
  • Variables are assigned with operators where the variable is on the left-hand side and the expression is evaluated on the right-hand side.
  • Variables do not need to be declared before the assignment.
  • Variables mentioned in PHP do not consist of intrinsic type- it means that a variable does not know in advance whether that will be used to store a number or a string of characters.
  • Default values are assigned to the variable that is used before the assignment.

Two main rules need to be followed while naming a PHP value. They are as follows-

  • Every variable name must start with a letter or an underscore character
  • A variable name can be made up of numbers, letters and underscores. However, the use of characters like+,-,%,(,),&, etc. is strictly prohibited.

29. State the differences between PHP4 and PHP5. [High-order thinking PHP developer interview questions]

PHP 4

  • All the constructors are assigned with the same name as the class.
  • Everything in PHP4 requires a value
  • It does not specify any class as an abstract
  • It does not consist of any static methods and properties in its class.

PHP5

  • Constructors are usually termed as_construct and destructors are named as _destruct()
  • Objects mentioned in PHP5 are passed through references
  • It allows assigning a particular class as an abstract class
  • It allows the use of static methods and properties in its class

[This is an ideal way to answer this OOPS interview question in particular. However, you can answer in your own words after understanding the core matter from the given answer.

30. Mention the method through which PHP and JavaScript and PHP and HTML could interact with each other. [High-order thinking PHP OOPS interview questions]

PHP and Javascript can never directly interact with each other. This is mainly because PHP is a server-side language while Java is a client-side language. However, an interaction can be formed if we exchange the variable in such a way that PHP can generate JavaScript code to be executed by the browser. This method makes it possible to pass specific variables back to PHP through the URL.

A PHP script can generate desired HTML and also it is possible to pass information from HTML back to PHP. As PHP is a server-side language while HTML is a client-side language, PHP works on the server side and interprets its result in the form of a string, array, or object. Then these results are used to display the values in HTML.

Intermediate OOPS Interview Questions

  • What is the need for OOPS?
  • What is a class?
  • What is an object?
  • Is it always necessary to create objects from class?
  • What is the difference between a structure and a class in C++?
  • What is the virtual function?
  • Are there any limitations of Inheritance?
  • What are the various types of inheritance?
  • Define a superclass.
  • What is the difference between overloading and overriding?
  • What are access specifiers and what is their significance?
  • What is an exception?
  • What is meant by exception handling?
  • What is meant by Garbage Collection in the OOPS world?
  • Can we run a Java application without implementing the OOPs concept?
  • What is Cohesion in OOP?

OOPS Interview Questions (MCQ)

1. _______ was the first language designed specifically for object-oriented programming.

  • Smalltalk
  • C++
  • PHP
  • Java

2. Who invented the first object-oriented programming language?

  • Adele Goldberg
  • Dennis Ritchie
  • Alan Kay
  • Andrea Ferro

3. Which of the following is not an essential aspect of OOPs?

  • Encapsulation
  • Polymorphism
  • Exception
  • Abstraction

4. Which feature of OOPs facilitates code reusability?

  • Abstraction
  • Encapsulation
  • Polymorphism
  • Inheritance

5. Which language among the following supports classes, but does not support the concept of Polymorphism?

  • C++ programming language
  • Java programming language
  • Ada programming language
  • C# programming language

6. What feature among the following is not right for OOPs?

  • Modularity
  • Efficient Code
  • Code reusability
  • Duplicate or Redundant Data

7. _______ is the feature of the Object-oriented programming model which allows one class to derive features from another class.

  • Inheritance
  • Data hiding
  • Encapsulation
  • Polymorphism

8. ________ is an object-oriented programming language but does not support all inheritance types.

  • Smalltalk
  • Kotlin
  • Java
  • C++

9. Which among the following operators can be used to show Polymorphism in CPP?

  • Overloading <<
  • Overloading &&
  • Overloading | |
  • Overloading +=

10. Which among the following does not show or cannot be used, to show Polymorphism?

  • Static member function
  • Constructor Overloading
  • Member function overloading
  • Global member function

How Can PHP Interview Questions for Freshers Help You Crack the Interview?

As a fresher in the PHP programming field, preparing for a technical interview can be overwhelming. However, practising PHP interview questions can dramatically improve your chances of clearing the interview and getting your desired job. Here are a few tips on how PHP interview questions for freshers can help you prepare for your interview:

  • Understand the basics of PHP
  • Learn about popular development practices
  • Prepare for frequent interview questions
  • Identify areas in which you can increase your expertise
  • Develop problem-solving skills
  • Communicate your views
  • Demonstrate your abilities as a PHP developer

Conclusion 

This brings us to the end of our practice PHP OOPS interview questions and answers blog. We hope that you can prepare yourself better with these object-oriented programming questions. Candidates are highly recommended to understand the purpose of the question asked during the interview before attempting.

Think twice before you give a final answer to any question regarding PHP. Keeping these things in mind and with a little cautious attitude you can nail any PHP OOPS interview questions. 

We hope this set of PHP OOPS interview questions for freshers has helped you prepare. Remember that the key to doing well in an interview is not strictly memorising answers, but also comprehending the principles underlying them. So, practise coding and experiment with various scenarios to solidify your understanding. With proper preparation, you can wow your interviewer and land your ideal job in PHP development.

For more information related to world web applications with PHP feel free to check out our related articles.

More Resources :

Full-Stack Developer Interview Questions for FreshersHirevue Interview Questions for Freshers
Data Entry Operator Exam Questions and AnswersJava Technical Architect Interview Questions and Answers

Frequently Asked Questions for PHP OOPS Interview Questions

Q1. What is PHP and what does it stand for?

Answer. PHP stands for Hypertext Preprocessor. It is an open-source server-side scripting language for web development that allows you to construct dynamic websites.

Q2. What are some common security vulnerabilities in PHP applications?

Answer. SQL injection, cross-site scripting (XSS), file inclusion vulnerabilities, and improper password storage are among the most frequent security flaws in PHP applications. To avoid these vulnerabilities, implement best practices such as prepared statements for database queries, input validation and sanitation, and secure password hashing techniques such as bcrypt. You should also update your PHP and web server software with security fixes.

Q3. What is the difference between GET and POST methods in PHP?

Answer. GET and POST are HTTP request methods used to send data to the server. The main difference between them is that the GET method sends data as a part of the URL, whereas the POST method sends data in the HTTP request body.

Q4. How do I prepare for an OOP interview?

Answer. To prepare for an Object-Oriented Programming (OOP) interview, you should study OOP principles, practice coding, understand design patterns, evaluate language-specific features, and be prepared to explain previous OOP projects. To demonstrate your proficiency, practice employing OOP concepts to solve problems and clear any misconceptions.

Q5. How do you answer OOPS concepts in an interview?

Answer. In an OOP interview, you should demonstrate your understanding of classes, objects, inheritance, polymorphism, encapsulation, and abstraction. Emphasise modularity, maintainability, and code reuse while offering real-world examples and discussing pertinent applications. Showcase how OOP principles can help with software design and development efficiency.

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