Top Web Development interview questions and Answers: Web Development Interviews are stressful and if you’re unprepared you may feel stressed and lose your confidence facing the person you interview. If you’re looking to excel during a web developer interview and are serious about making your career in web development, it is essential to be prepared for the most frequently asked interview questions and answers related to the field.

This article designed by Techstack Academy offers the most popular web development questions and answers for experienced candidates to help you get through the next job interview.

As Full Stack Development has risen to become a market that is worth billions of dollars and counting, it’s no surprise that this leads to a huge variety of job openings around the globe. When it comes to working in the field, you should have the practical knowledge as this field is dependent upon the practical development part.

Top Web Development interview questions and Answers
Top Web Development interview questions and Answers

Like we said, there comes an abundance of competition, which makes the interview process a bit difficult too. Our article has carefully selected the best questions with the highest likelihood of appearing during an interview. Take your time studying these and learn the best way to approach questions and respond efficiently.

It is beneficial to master the basics of technology before attempting an interview in order to advance your career. The demand for web development and PHP is increasing day by day and people are looking for the right institutions to have the best knowledge to clear the path of their success to become successful web developers.

It’s now time to fill out an application and to interview for tech-related positions. If you are a fresher or an expert professional and looking to change your career towards web development or PHP development. We’ll help you in case you’re not sure what to tell an actual hiring manager. 

Interviews for jobs in web development aren’t too scary If you’ve familiarized yourself with the most frequently asked questions, and some unexpected ones. Our academy always tries to help in every possible way to clear the road of success for their students.

That is why we have this list of most frequently asked web development questions and answers to help you out. Additionally, we have suggestions and tips on how to prepare and respond to these questions. It is crucial to acquire the certifications in web design that you require to impress and be prepared for an interview.

Techstack Academy offers different web development courses for freshers and expert professionals and covers almost every topic which is required to make you a web developer like HTML, CSS, Javascript, Reactive Designing, PHP, Database, Graphic Design and many more.

The course covers every aspect of the subject, and provides students an understanding of how to create web applications, shopping carts that have impressive designs. The course will be led by our expert trainers with internship programs that will help you improve your abilities. Techstack Academy is a reputable web development institute located in Delhi which provides a deep understanding in web development courses.

How can I prepare in advance for a web development interview?

Follow these impressive tips and guidelines to prepare yourself for the web development interviews and jobs:

  • Review your resume and take the time to read it through. Even if you’re aware of the information that you’ve included on your resume, think about revisiting it in order to review your accomplishments of projects, awards and previous work tasks. This will help you feel more prepared to respond appropriately.
  • Test it with your trusted friend or family member or the person who has a reputation as a trustworthy person or former coworker might help you practice your interview with. They can provide comments on the answers you gave, as well as the way you conduct yourself in the mock interview so that you can improve your performance and be more prepared for your interview. Following this, you’ll feel confident in your answers.
  • Make your portfolio according to your experience and work you have done. If you don’t have any portfolios, consider creating one to show the manager who will be hiring you. In the world of web design, it’s crucial to outline your past projects, work and journeys to show your capabilities.
  • Get yourself up-to-date with the industry updates. Read news articles or blogs, as well as listen to podcasts that are related to web development to make sure you’re in the know about the latest trends. If you’re giving an interview, you must be aware about the latest trends in the field and responsibilities.

This is a list of the most frequently asked questions on Web development.

Top Web Development Interview Questions And Answers

Q1. What is Web Development?

Web development, sometimes referred to as website development, is the work involved in making, building and maintaining websites and web-based applications that operate using the browser. However, it could also encompass the design of websites, Web programming and managing databases.

Web development can encompass a range of different types of web-based content. A few examples are hand-coding websites using the text editor, creating an online site using software such as Dreamweaver and the updating of a blog using blogs on a website.

Web developers develop and maintain websites. They also are responsible for the technical aspects of the site like its capacity and performance that are indicators of the speed of a site and how much traffic it can handle. Additionally, web developers can make content for the site.

Q2. What is CORS? And how does it work?

Cross-Origin Resource sharing (CORS) can be described as an HTTP-based protocol which allows servers to declare any source as domain scheme, domain or port different from its own that the browser can allow loading of resources.

It lets you make requests from one site to another site in the browser that is typically restricted by a different browser policy known as the Same-Origin Policy (SOP).

The Cross-Origin Resource Sharing method that permits a variety of sources like JavaScript, fonts, etc. on a webpage to be accessed via a domain that is not the one from which the resource came. It’s a mechanism that’s supported by HTML5 which manages the XMLHttpRequest connection to a domain which is not.

Q3. Explain Pseudo-class.

It’s an CSS technique that determines the style whenever an element changes its appearance. E.g. styles change when you hover your mouse or hover over a link, different styles for visit or visited links for example, and more.

There are four kinds of pseudo-classes:

  • Link pseudo-classes are used to design the link in both its default state as well as when it has been visited.
  • Dynamic Pseudo-classes that are dynamic can be used to any element in order to determine how they will be displayed when the cursor is on them or clicking on them, or after they have been selected
  • Structural pseudo-classes permit to design elements based on the exact numerical location of an element
  • Other Certain elements can be styled in a different way depending on the language used or the kind of label they’re not.

Dynamic Pseudo-classes:

:link: It is the Link and it has the value of the href attribute is not in the history.

:visited: It is the link visited and it has the value of the href attribute in the history.

:target: It is the target link and it has the value of the targeted link.

:active: It is the active link and it has the element that has been clicked.

:hover: It is on when the cursor is over the element.

:focus: It is the element that captures the focus of the document.

Structural and other Pseudo-classes

:root: It is the main element of a document.

:empty: It does not have child nodes

:only-child: It has no sibling nodes

:only-of-type: It has a unique selector among its siblings.

:first-child: It is the first child node of another element.

:nth-of-type(n): It is the nth element with that selector.

:last-child: It is the last child node of an element.

:first-of-type: It is the first element of its selector type in the parent element.

:last-of-type: It is the last element of its selector type in the parent element.

:lang: It has a specifically defined language code.

:not: You are not using a specific selector

Q4. What is the difference between SOAP and REST?

SOAP makes use of XML to exchange messages however REST isn’t restricted to XML and it is the option of the implementer on which Media-Types to utilize, like XML, JSON, Plain-text. Additionally, REST is able to use SOAP protocol, however SOAP is not able to utilize REST. SOAP specifies its own security. RESTful web services obtain security measures from the transport that they are based on. SOAP allows XML data format , but only. REST allows different formats for data like Plain text, HTML, XML, JSON and so on.

Q5. What is an ETag, and what is its function?

An ETag (entity tag) is an HTTP header utilized to ensure that the user is the most current version of the record. When a GET request is sent, ETag is used to verify that the ETag returns as an HTTP response header. The ETag can also allow the user to make requests that are conditional.

The process by which ETags are generated hasn’t been described within the HTTP specification. The most common methods for ETag generation are the use of a collision-resistant hash function that is part of the content or a hash of the time stamp that was last modified or even the revision code.

This allows caches to improve efficiency and reduce bandwidth since web servers do not require resending a complete response if content was not modified.

Q6. What is the functionality of the browser?

Browsers have a variety of options. They include:

  • It allows you to access HTML pages as well as all the web elements that are used in web-based apps, different websites and also display responses from other websites in response to inquiries.
  • Web search allows you to find the website you are interested in by typing the URL or URL in the address bar, and then viewing the results using one or all of these search engines.
  • Navigation controls are utilized to go back to recently visited pages using the back button, and then the next button to advance.
  • History records the websites you have visited according to chronological time. It lets you bookmark sites that you are interested in to revisit or browse at a later time. It can also save previously visited websites by storing them in caches and makes visitors recognized by websites, allowing the access to the sites easier.
  • Manages passwords for commonly visited websites that require authentication. It will typically keep users already logged in to the account.
  • Allows access to various websites and exchange information through API calls, communications by email, information and media file sharing software.

A sample of browsers Internet Explorer, Mozilla Firefox, Google Chrome, Opera, Safari.

Q7. What is equality in javascript?

Javascript is a scripting language and provides unique client side scripting to users. It has both strict and type-converting comparisons.

Strict Comparison (===): This comparison checks for value equality without allowing coercion. 

Abstract Comparison (==): This comparison checks for value equality with coercion allowed.

These are some simple equality rules:

  • If any of the values in a comparison could be a true or false value, avoid using == and use ===.
  • If any of the values in a comparison could be specific values 0, “”, or [] means empty array, you should avoid using == and use ===.
  • In all other cases, you can use ==. Because in all other cases it can simplify your code to improve readability.

Q8. What is W3C and why is it important in coding?

W3C is the abbreviation for World Wide Consortium and it is an international organization which focuses on standardizing and developing the internet.

As a web developer adhering to these standards will ensure that content from the internet is available to all browsers in order to reach everyone and also enhances your user’s experience. For instance, using W3C compliant CSS and XML ensures that all websites perform similarly, and also increases SEO.

Q9. What is the importance of namespaces in web development?

Namespace is mostly utilized in programming languages, in which the same name could be applied to different objects. It is designed to bring names that could be used elsewhere in the same or interlinked programming as well as objects and elements.

Namespaces are simple global objects used to store properties, methods and other objects within them. It improves user-friendliness by allowing modularity giving users the possibility of reusing the code and avoiding name conflicts.

Namespaces in computer programs are generally employed to aid in creating a grouping of identifiers and symbols in a specific functionality, and to prevent name collisions among names that have the identical name.

Q10. What are some tips developers use to reduce the load time of web applications they have designed?

The speed at which your website or application loads initially will be the very first impression that your users receive. The time from the moment your client or user clicks the domain name of your website to the moment they view your content is the most crucial time frame you can use to create a great first impression.

Certain of these techniques are ones that can be used on the front-end while others are implemented in the back-end. Whatever the case, web applications must be loaded swiftly.

Take the appropriate measurements: The first thing to accomplish is to include measurements. There are numerous stages in loading, so you’ll never determine where the bottleneck is when you don’t measure the proper segments.

Following are the top crucial steps in the loading process:

  • Browser requests your page.
  • Response received
  • Largest contentful paint
  • Response served
  • First contentful point
  • Time to interactive

Codes to reduce: Once you’ve got measurements, you can start creating optimizations. Optimizations can be a trade-off and measures will reveal which ones are worthwhile.

The most speedy page to load is a blank page however, lots of code could be added into an application before users discern the difference in speeds between the app and the blank page.

The most common thing is that the changes are so small that you don’t notice the difference between building to build until the day comes when it gets slower. It’s obvious that your application is excessively bloated. It’s the moment to reduce the amount of code that can make a difference.

There are two gains in speed when you cut the code:

  • Your app gets transferred across the network more quickly.
  • The browser’s user’s browser is able to process the code faster.

Split code into chunks: After you have eliminated the amount of code is possible in your application You can consider the possibility of decreasing the code that is required to load the initial application. 

Let’s say that 20 percent of your code drives a feature in your application that users only access after just a couple of clicks. It’s a waste of moment for the web browser to process the code prior to displaying the loading screen. By breaking your code down into smaller chunks, you can drastically reduce the amount of time required to interact with.

Server-side render: Since browsers have to perform all the intensive compiling and parsing as well as having users using Chromebooks as well as mobile devices, a popular method to speed up loading times is to let your servers handle some of the load. This means that instead of providing the user a blank page, then employing Javascript for filling in all of the information, which is what most single-page apps nowadays it is possible to use an Javascript engine in your web server (usually Node.js) to fill with as much data and information as you want to.

Compress assets: Assets are among the most hefty components of an application. Images can be loaded multiple megabytes and loading multiple icons can easily override the browser’s maximum number of concurrent requests which can result in a massive load of waiting.

It is almost impossible to download an image from the internet only to reference it in an app. Images must be scaled to the smallest dimensions they can be displayed at. If you have a profile of a user which is displayed in tiny 50 pixels by 50-pixel size, but not changing the size, your application will download the entire image which appears sharp and professional as wallpaper for desktops and then shrink it into the tiny dimensions.

Second, images can be compressed in accordance with the format they are in. Today, webm is the most popular format, however compressing available on the internet is continuously being refined and new formats are in the coming. Due to the ever-changing format, certain browsers may not be compatible with the latest formats! However, the technology of browsers can let users’ browsers load in any format they are able to support.

Therefore, you should compress to the most recent and best format, but preserve a less current version. Also, use images or video elements that can support the older formats.

Q11. What factors do you consider taking into consideration SEO maintenance, UX, security, and performance when building an online application?

Analyze everything in your web application. Explain to your interviewer how you prioritize your actions in line with the demands of the company. If your company handles important information, then security should be the top priority. If it’s an online company of medium size, SEO and UX might be top of the list and on.

Q12. What is scope in javascript and what are different types of scopes?

Scope of JavaScript is the context in which JavaScript is running code which decides on the availability of the variables JavaScript. Every function creates a brand new scope.

Variables that are defined within the function aren’t accessible (visible) by anyone else in the function. A thorough understanding of these concepts will allow you to write more efficient, better and cleaner code. This will aid you in becoming an improved JavaScript developer.

What is the significance of Scope?

  1. The primary advantage of having a scope is the security. The variables can be accessed by only one specific area within the application. By using scope, we are able to keep out any unintentional modifications to variables that are accessible from other areas in the application.
  2. This also helps reduce namespace collisions. This means that we are able to use the same names for variables in multiple scopes.

Scopes of Scope

There are three kinds of scopes in JavaScrit:

1. Global Scope: Any variable that’s not part of any block or function (a set of braces curly) is within global scope. The variables that are in the global scope are accessible from any place within the program. 


Var say = ‘Hello World!”;

Function hello() {



// It will print ‘Hello World!’


2. A Local Scope (or Function Scope): Variables declared within a function are in its local scope. They are only accessible by the function within it and cannot be accessed via external code. 


Function hello() {

Var say = ‘Hello World!”;



// It will print ‘Hello World!’


//uncaught ReferenceError: display is not defined console.log(display);

3. Block Scope: ES6 added lets as well as const variables. However, unlike the var variables, they are able to be mapped to the closest couple of curly braces. They can’t be accessed outside of the curly braces. 

For instance:


Let display = ‘Hello World!’

Var lang = ‘English’;

Var say = ‘Hello World!”;

console.log(display);   //It will print ‘Hello World!’


// Prints ‘English’


//Uncaught ReferenceError: greeting is not defined console.log(greeting);


It is evident that variables such as var variables are able to be used in a different block, which can be said to mean that the var variables aren’t block-scoped.

Q13. What is the importance of HTML5, CSS3, Javascript in web development?

  • HTML is an independent platform and browser markup language using a number of tags that create the basic structure of an internet page.
  • CSS enhances the layout of pages and the content with style.
  • JavaScript controls the behavior of web elements, and thereby makes your website interactive/responsive, validates user input values, captures website visitor’s information and recognizes previous visitors, help in analyzing the percentage of blog post visitors’ click-through rate.

Q14. What’s the point of the alt attribute on images?

Alt attribute provides alternative information for images. alt attribute is a substitute to an image, in case the user is unable to view it. Alt attributes should be used to describe images. alt attribute is used to describe any image other than those that are used for as a decoration or for display purposes, in which case it should be left blank.

The src attribute must be present and includes the URL of the image you wish to embed. Alt attribute includes a text description of the image. This isn’t required, but it is extremely beneficial to make the image accessible to screen readers. They will read the description to their users to let them understand what the image signifies.

Alt text will also be displayed on the page in case the image isn’t loading because of a problem, such as for instance, network issues or content blocking. 

Q15. What are the advantages of using HTTP/2 and the HTTP 1.1?

Understanding if a candidate is aware of the major differences and benefits of using HTTP/2 will show their understanding of the subject which will help you understand the ways in which their approach will be compatible with the role of a web developer. What are the indicators to look for in a response:

  • The overall knowledge of HTTP
  • Recalling specific information
  • An insight into their method of operation


“HTTP/2 was created to enhance performance of web-based applications. Web developers can be amazed at how it can make applications more efficient and speedier by reducing load time and improving the communication between servers and browsers. I’m a firm advocate of HTTP/2 because I’ve looked at data and discovered how HTTP/2 could reduce the time it takes to load a page by as much as 20%.”

Q16. What is the use of canvas in HTML5?

Canvas was added as a feature in the current version of HTML5 to give users the ability to draw graphics on the go with the help of scripting language JavaScript. You can try various methods with < canvas > to allow for the drawing of paths, circles, boxes, images, and more.

You can add a creative level of interactivity in your web pages with the help of the CANVAS element because now you can control the graphics, images, and text dynamically with a scripting language. The CANVAS element helps you turn images, photos, charts, and graphs into animated elements.

If your audience is primarily using Windows XP and IE 6, 7, or 8, then creating a dynamic canvas feature is going to be pointless since those browsers don’t support it.

Q17. What is the difference between cookies and local storage?

Cookies: The data is available both on the both the server and client sides. The data is transmitted to the server side with each cookie request. The storage capacity of cookies is 4095 bytes per cookie. Cookies expire, and cookie data is deleted after a certain period of time.

Local Storage: Only on the local side of the browser, information is available. The server cannot access local storage until it has been explicitly requested by the server through either GET. Storage capacity for local storage can be 5MB for each domain. The storage has no time limit date and must be removed manually.

Q18. Explain ID and classes concepts in CSS.

The CSS language uses class and ID selectors. CSS, class and ID selectors are used to distinguish the various HTML elements. The major advantage of setting the class or ID is the ability to present the identical HTML element in a different way, based on the ID or class it belongs to.

Class selector: Class selector the class selector is used to select elements with specific class attributes. It matches all HTML elements by the contents of the class attribute. This . symbol, together with the class’s name is used to choose the class you want to select.



/* Give your properties here*/


ID selector: This selection of ID is able to match an element on the basis of the values of its ID attribute. To allow that element’s ID attribute to be picked the ID attribute of it must precisely match the value specified to the chooser. In order to select an element, the symbol # symbol as well as the ID from the HTML element’s names are utilized to choose the element you want to select.



/* Give your properties here*/


The distinction between ID and Class selector

The main difference of an ID from the class is that an ID is used only to identify a specific element within our HTML. IDs are only utilized to identify one particular element of the page that needs to be styled in a specific way to it. But, a class could be used to distinguish multiple HTML elements.






Background-color: #FFAFA4;



Background-color: #DEDAF7;





<div class=”main”>

<h3>Welcome to Techstack</h3>

<p id=”demo”> Your paragraph text with an ID</p>

<p> Other paragraph with no id </p>




Q19. What is a document object model?

Within the Document Object Model, documents have a logical structure that is very similar to trees; to be more specific it’s like an “forest” that could contain multiple trees. But document Object Model does not specify that documents should be created as trees or groves and does not specify how relationships between objects are executed in any way.

The object model defines the logical model of the programming interface that can apply in any manner that a specific implementation finds useful. The specification we provide utilize a structure model, for the representation of documents that resembles a tree.

We specifically stay clear of terms such as “tree” as well as “grove” to avoid suggesting a specific implementation. One of the most important properties that is a hallmark of DOM structures models includes structure isomorphism, that is, if Two Document Object Model implementations are used to build an image that is identical to the document they will produce the exact same structure model using exactly the identical objects and relationships.

The term Document Object Model was chosen as its object model is employed in the conventional object-oriented design sense. Documents are constructed using objects and the model includes not just the structure of the document, but also the way in which it behaves documents and the objects from which it is made.

The nodes of the diagram above don’t represent the structure of data, but represent objects that have identities and functions. As an object model this Document Object Model identifies:

  • the interfaces and objects that are used to create and manipulate a document
  • the meaning of these interfaces and objects, including attributes and behavior
  • the interrelations and collaborations between the objects and interfaces

The format of SGML documents is typically described through an abstract data model and not the concept of an object. In an abstract model the model is designed on the information.

In programming languages that are object-oriented the data itself is contained in objects that protect the data from it from direct manipulation by external sources. The functions that are associated with these objects define how objects can be altered, and they form an integral part of the model for objects.

The Document Object Model currently consists of two components, the DOM Core and the DOM HTML. 

Q20. What do you understand about frameworks?

Since they are usually developed, evaluated, and then optimized by skilled programmers and software engineers Software frameworks are flexible as well as robust and efficient.

Utilizing a framework software for developing applications lets you concentrate on the higher-level features for the program. This is because all lower-level functions are handled by the framework.

Software frameworks ease the work for developers, allowing them to manage the entire process of developing software or, at the very least on one platform.

The benefits of using a computer framework

  • Helps establish more efficient programming practices and making to the use of design patterns
  • Coding is more secure
  • Code that is redundant and duplicated is possible to avoid.
  • It helps to ensure consistency in the development process and less bugs
  • It makes it easier to work on advanced technologies.
  • One can create their own software framework or contribute to open source frameworks. Therefore there is an ongoing enhancement in the performance
  • A variety of code components and functions are built and tested before being released to the public. This ensures that applications are more secure.
  • Debugging and testing the code is much more simple and can be completed with the help of developers that don’t have the code
  • The time needed to create an application is significantly reduced.

Q21. What are the various HTTP methods that are supported by Restful Web Services?

These are some of the Restful web services which supported HTTP methods are:

  • GET
  • POST
  • PUT
  • DELETE and
  • HEAD

Q22. As a developer, which languages are you proficient in?

HTML, CSS, SQL, PHP, Ruby, Python and JavaScript are some of the more popular programming languages that web developers must be able to master effortlessly. You can check your efficiency by taking different tests for technologies. These questions will provide insight into the candidate’s background as well as their preferences, strengths and weaknesses. What should you find in an answer?

  • Experience with programming languages
  • The level of interest for certain languages
  • The role is appropriate and the Company


“I’m adept at HTML, CSS and PHP. I also have a beginner’s skills of SQL as well as JavaScript. I’d love to broaden my web development skills by adding Python which is why I’m currently looking into the best Python course during my spare time.”

Q23. What are some of the new features of CSS3?

CSS3 has resulted in a number of modifications that have made the framework more user-friendly as well as powerful. CSS integrates with HTML and gives the basic design and style for websites. CSS3 is the most recent version of CSS.

CSS3 includes JavaScript along with mobile application development capabilities, along with features like gradients, transitions and much more. The features that have been added to the system and are frequently used include:

When CSS3 codes are written using CSS it is invalid. CSS3 makes web pages more appealing. It is quicker to make an attractive page.

  • CSS3 is the most recent version that has a responsive design.
  • CSS3 could be broken into modules.
  • In CSS3 animations and 3D transforms are employed. The elements are moved around the screen by means of JavaScript and Flash. When using elements, they can also be set to alter their size and the color. All sorts of changes as well as motions are done using CSS3.
  • In CSS3 the designer writes the code in the form: round border border-radius: 20px.
  • They are not being delivered by any server, nor did they carry out any other actions. Gradients can also be created using the code gradBG.
  • In CSS3 the developer can add the text shadows in order to make the process simple and efficient. They also add words for effect of visuals on the breaking line as well as an appropriate fit inside the column. The font size changes and the color of text.
  • CSS3 is compatible with HSL RGBA, HSLA and the gradient colors .
  • CSS allows simple text blocks.
  • In CSS3 the list item is counter, which is affected by Counter increment properties and the counter reset property.
  • In CSS the use of lists within a CSS3 display, the display’ property has to include a list of properties within it.
  • CSS3 does not accommodate numbers in a system.
  • The property list style allows an image to be set against the style marker. It can be set inside or outside the box.

Q24. What do you know about sessions in PHP?

Sessions within PHP is a method used to store data that will be shared across several pages on an entire website. The data is not saved on the computer of the user unlike cookies. On the servers, in a temporary folder the file is generated by the session in which the session variables that are registered and their values are saved. The information will be accessible to all pages of the site during the visit.

If you’re working on applications, you launch it, make some changes after which you close it. It’s similar to a Session. The computer recognizes what you’re doing. It is aware of when an application is initiated and shut down by you.

On the web the web server doesn’t recognize who you really are, or what you’re doing because the HTTP address isn’t kept in the state of. This issue can be solved with session variables that store details about the user that can be used across different pages (e.g. username, favorite color, etc).

The default session variables will remain in place up to the time the user quits their browser.

So Session variables store only the information of a single user and are accessible to all pages within an application.

Q25. What is inheritance and is multiple inheritance supported in PHP?

Inheritance in OOP is when a class is derived from a different class. The child class inherits all the protected and public methods and properties of that parent class. Additionally, it may possess its own methods and properties. A class that is inherited is defined through the word extends.

Inheritance permits a class to reuse the code of another class without having to duplicate it. In inheritance, you’ve got a parent class that has the properties, methods and even data, while the child class is able to use the code of that parent class. This is why inheritance allows reuse and is a key idea of OOPs.

Inheritance comes in three forms: single, multilevel and multiple. PHP can only support single inheritance, meaning that only one class is resulted from a single parent. It is possible to simulate multiple inheritance with the help of interfaces.

Single Inheritance: A single inheritance is a term used in PHP where only one class is passed on to a single class. There must be two classes between this process. The first is that of the basic course (parent class) as well as the other an individual child class.

Multiple Inheritance: Multiple Inheritance in PHP are the resources of Object Oriented Programming Languages in which subclasses and child classes are able to inherit from superclasses or multiple parent classes.

Multilevel Inheritance: PHP allows Multilevel Inheritance. This kind of inheritance has more than two classes. In this kind of inheritance the parent class is inherited by the child class, and that child class will be passed on by the class of the child. This kind of inheritance in the PHP language is exactly identical to C++ etc.

PHP can only support one inheritance, which means that a class may be extended only from a single class by using the word extended.

Q26. How many types of variables are there in php and explain their characteristics.

There are eight types of data in PHP that are used to create the variables:

  1. Integers: These are the whole numbers with no decimal point like 4195.
  2. Doubles: These are floating-point numbers such as 3.14159 or 49.1.
  3. Booleans: These are a type of Boolean that have just two possibilities for values – real or fake.
  4. NULL: It is a particular type with only one value Null.
  5. Strings: These are a sequence of characters, for example PHP can support string operations.’
  6. Arrays: These are names and indexes of different values.
  7. Objects: These are instances of classes that are defined by the programmer, and can be used to package different types of values as well as functions that are unique in the specific class.
  8. Resources: These are a special variable that contain references to resources outside of PHP.

The most important features for PHP variables are:

  • Every variable in PHP is identified by the leading dollar symbol ($).
  • The value of a variable is the sum of the values of the current assignment.
  • Variables will be assigned by using an = operator placing the variable placed on the left side, and the expression to be examined in the middle.
  • Variables may be declared, but they do not need to be declared before assigning.
  • Variables in PHP don’t contain specific types and do not know ahead of time which one it will use to store a number , or an array of characters.
  • Variables that are used prior to being assigned are assigned the default values.

Q27. Give the name of some popular content management systems (CMS) in Php.

  • WordPress: WordPress, an open source and free-of-cost CMS for managing content (CMS) that is based on PHP and MySQL. It has a plug-in structure and a template system. It’s mostly associated with blogging, but also allows other types of content on the web, including regular mailing lists as well as forums, media displays along with online storefronts.
  • Joomla Framework: Joomla is open-source and free CMS to distribute web-based content. It is developed by Open Source Matters, Inc. It is based on a model-view-controller web application framework that can be used independently of the CMS.
  • Magento: Magento is an E-trade software that is open source created by Varien Inc., which is a great tool for business online. It features a flexible and designed design that is scalable with a variety of control options that can be beneficial to clients. Magento uses the E-trade stage, which provides organizations with extensive E-business plans and a vast support network.
  • Drupal: Drupal can be described as an out of the box web-based tools for managing content and an adaptable platform to assist you in creating the perfect tool to support your strategy for managing content. Technology and business leaders utilize Drupal to develop real-world solutions for enterprises that enable the web to innovate.

Q28. What are type casting and type juggling?

Type Casting: In the process of typing casting, a data type is transformed into another kind by the programmers by using the casting operator in the programming design. It is utilized in computer programming to ensure the correct processing of variables by functions. Typecasting can be described as the conversion of an integer into the form of a string. To convert something to typecast, place the type of variable you wish to use within parentheses of what is actually the variable. (char)a makes “a” function as a character.

Example: $str = “10”; //$str is now string

$bool = (boolean) $str; //$bool is now boolean

Type Juggling: Type juggling refers to using the variable type. In PHP the term “variable type” refers to the context within which it is employed. When an int value gets assigned to a variable it will be converted to an integer. If an integer value is associated with the variables, that value will become an String. PHP doesn’t support data types for variables. The type of the variable gets altered automatically depending on the value assigned to it. This is known as type juggling.

Example: $val = 5;  //$val is now number

$val = “500”  //$val is now string

Q29. What are null and constants in PHP?

Null in PHP: Null is an exclusive kind of data in PHP that can only have one value, which has the value NULL. A data type variable NULL doesn’t have any associated value. Any variable may be empty by assigning the value NULL on the variable.

Syntax: $var == null; or $var == NULL;

Constants in PHP: A constant can be described as an identification (name) to identify a basic value. The value is not able to be changed in the script. The name of a valid constant begins with an underscore or letter (no $ before the name of the constant). Contrary to variables, constants become universal across all scripts. If you’ve defined an undefined constant, it can never be altered or changed. To define a variable, you must utilize the create() function and then to find what is the worth of a variable it is as simple as defining the name of the constant. As opposed to variables, you don’t require a constant that has an $.

A define() function defines the term “constant”. Constants are similar to variables, with the following reasons the value of a constant can’t be altered after being established. Constant names do not require an introductory dollar symbol (“$”) Constants are available regardless of their scope.

PHP has some predefined constants:

_METHOD_: This represents the class name.

_CLASS_: This returns the class name.

_FUNCTION_: This denotes the function names.

_LINE_: This denotes the working line number.

_FILE_: This represents the path and the file name.

Q30. What will be the final output of this program and explain why?


echo $x;

echo “<br/>”;

echo $x+++$x+++;

echo “<br/>”;

echo $x;

echo “<br/>”;

echo $x—$x—;

echo “<br/>;

echo $x;

The output of the above program will be:






Here are two important reasons:

  1. The expression $x++ specifies that you use what is currently in the $x– then increase it. The same way, the expression $x specifies that you use the value currently used by the $x as the basis for decrementing it. then decrease it.
  2. It is the case that an increment operator ( ++) is more important than its sum counterpart ( +) in the order of operations.

In light of these factors it is clear that the value of $x +++$x++ is evaluated in the following manner A first mention of $x occurs when its value is 5 (i.e. before it gets increased) The second one happens after its value has reached 6 (i.e. prior to when it is incremented again) The result equals 5 + 6,, which results in 11. Following it has been done, the price is 7 and the value of “$x” is 7 because it was incremented twice.

Similar to this, we understand that the value of $x —$x–is evaluated in the following manner the primary reference of $x occurs when its value remains 7 (i.e. prior to when the value is incremented) The second one happens after its value has reached 6 (i.e. prior to the time it’s decremented once more) The result is 7 – 6 , which results in one. Following this process it is apparent that $x’s value $x is returned to its initial value of 5, as it was incremented two times and then decremented two times.

Q31. How PHP and HTML interact with each other?

PHP scripts are able to create HTML as well as they can transfer details to and from HTML in PHP. PHP is a server-side programming language while HTML is a language that is client-side. Thus, PHP executes on the server and returns its results in arrays, strings, objects and we employ them to display their values in HTML.

This interaction can bridge the gap and utilize the most effective two languages.

Q32. How PHP and Javascript interact with each other?

JavaScript is the client-side scripting language, and PHP is the scripting language used by servers. JavaScript is utilized as a client side to verify information about the client. PHP is the server side that is utilized to communicate with databases. When using PHP, HTML is used as a string within the code. To display it in the web browser, we write JavaScript code in the form of strings in PHP code.

JavaScript is not able to directly communicate with PHP because PHP is always executed by the server first and then transmitted to the browser of the client. JavaScript is able to only send data to PHP.

Q33. Explain the concept of constructor and destructor in PHP.

A constructor lets you initialize the properties of an object upon its creation. If you make an object using the constructor using the __construct() method, PHP will automatically call this function every time creating an object using the class.

Constructors are identical names as class or struct and typically begin with the data members of the newly created object. The following illustration shows a class called Taxi is constructed using a basic constructor. The class is then created by using the new operator.

To call the constructor of the parent class from the constructor of the child class, you use the parent::__construct(arguments) syntax. The syntax to call the constructor of the parent class is identical to a normal method.

A destructor will be used when an object is destroyed or the script has been stopped or closed. If you write the destruct() procedure, PHP will automatically call this function at the end of your script. It is important to note that the function destruct begins by using the two underscores (__)! Destructors typically are employed to manage memory allocation and perform other cleaning for a class object as well as its members of the class when an object has been destroyed. A destructor is used to deal with an object of a class when the object is removed from scope or is removed explicitly.

Example of Constructor and Destructor

<?php class classname { private $name; private $link; public function __construct($name) {$this->;name = $name;


Public function setLink (classname $link){

$this->;link = $link;


Public function __destruct() {

echo ‘Destroying: ‘, $this->name, PHP_EOL;




Q34. What is array and how many types of arrays used in PHP?

The array that is used in PHP could be an organized map. Maps are a type which associates keys with values. It is designed for a variety of uses: it could be referred to as an array or list (vector) as well as amish tables stack, dictionary, collection queue, and perhaps many more.

If you’ve got a checklist of things (a list of the names of cars such as) then storing them in a single variable could appear like this:

$cars1 = “Volvo”;$cars2 = “BMW”;

$cars3 = “Toyota”;

But, what happens if you want to go through the cars to find one specific car? What if there were not three cars however, but 300?

The solution is to build an array!

An array may contain many values under one name. You can get the data by using the index numbers.

In PHP array() function is used in PHP. array() function is used to create an array.


In PHP there are three kinds of arrays:

  • Indexed arrays – Arrays that have the numeric index
  • Associative arrays – Arrays that have named keys
  • Multidimensional arrays – arrays that comprise an array or arrays

Q35. How can you make connections with databases in php and how do you retrieve data from MySQL databases in php?

You need to use MySQL hostname and username and password in order to create a connection to the MySQL server using the mysqli_connect() method or declaring the database object of the mysqli class.

Code Sample:

$mysqli = mysqli_connect(“localhost”,”username”,”password”);

$mysqli = new mysqli(“localhost”,”username”,”password”);

There are many functions available in PHP to pull information out of databases like the MySQL database.

Some functions are described below:

A) mysqli_fetch_array() – It is used to get the records in numeric arrays or an array that is associative.

Code Sample:

//Associative or numeric arrays



echo “Name is $row[‘email’0”;

B) mysqli_fetch_row() – It is used to retrieve the records from the form of a numeric array.

Code sample:

//Numeric array




C) mysqli_fetch_assoc() – It is used to retrieve the records from the form of an array that is associative.

Code sample:

//Associative Array




d) mysqli_fetch_object() – It is used to fetch the records as an object.

Code sample:





Q36. What is the working of ‘foreach’ loop in PHP?

A foreach expression is a looping technique employed in PHP to repeat the loop of the type array. The operation of foreach is quite simple. Each time you pass the value, elements are assigned a value and the number of pointers are increased. The process continues until the completion of the array.

The following syntax is for the foreach expression in PHP:



Code inside the loop;


Q37. What is PEAR in php?

The PEAR (PHP Extension and Application Repository) is a framework and repository of reused PHP components. PEAR is a repository for code with all kinds of PHP code snippets , libraries and code.

PEAR also has a command line interface which is able to automatically install the packages.

Q38. What are the main types of errors?

The three main kinds of errors that occur in PHP are:

  • Notices: Notices aren’t critical errors that could be encountered in the course by the program. They aren’t accessible to users. Example accessing an undefined variable.
  • Warnings: are more important than warnings. Warnings do not interrupt execution of the script. They are, by default, evident to the users. For example: Include() the file which isn’t there.
  • Fatal Errors: It is the most severe error type that is the case when it occurs. It immediately stops the process of execution. Example accessing a property in a nonexistent object or requiring() the existence of a file.

Q39. Explain the difference between runtime exceptions and compile time exceptions.

An error that occurs during the time of compiling is referred to as an unchecked exception. This type of exception is not to be ignored, and must be dealt with in a careful manner. For example, if you use FileReader class to read data from the file and the file specified in class constructor does not exist, then a FileNotFoundException occurs and you will have to manage that exception.

To accomplish this you’ll need to write your code inside a try-catch block and deal with the exception. In contrast the exception that happens during runtime is referred to as unchecked-exception.

Q40. What is $_SESSION and why do we use Php session_start() and session_destroy() function?

A session is a creation of a file in a temporary directory of the server on which session variables as well as their session IDs are kept. The information will be accessible to all pages of the site during the session.

The space for the temp record can be managed by a setting within the php.ini document referred to as session.save_path.

When the session begins, the events that occur

  1. PHP first makes two duplicates of one of a kind session id for that particular session of the client which is an arbitrary string of 32 hexadecimal numbers, for example, 3c7foj34c3jjhkyepop2fc937e3443.
  2. One copy of the unique session ID is automatically sent to the computer of the user to ensure the synchronization of future sessions. One copy is kept on the server level until the session has started.
  3. When you need to visit the page of a web application or website the session ID of the user currently logged in is associated with the HTTP header. This will be compared with the session ID that is stored on the server. After the comparison process is completed it is possible to access the webpage of the web app or the website.
  4. A session will end at the time that the browser is closed by their browser. If the user leaves the website the server will close the session at the end of a specified time, usually 30 minutes in duration.

PHP session_start() function is used to begin the session. It either starts a fresh session or resumes the session currently in progress. It returns the session, if it has been established already. If the session isn’t in existence, it will create and then return sessions.

Some Additional tips for Web Development Interviews

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