PHP Javascript MCQ Inteview questions for Mettl Test

1. What is the purpose of the spl_autoload_register function in PHP?
a. To define a constant
b. To register custom autoloading functions
c. To include external libraries
d. To autoload classes when they are used
Answer: b. To register custom autoloading functions

2. Which of the following PHP magic methods is called when an object is serialized?
a. __serialize
b. __serializeObject
c. __serializeData
d. __sleep
Answer: d. __sleep

3. What does the trait keyword represent in PHP?
a. A design pattern
b. A reserved keyword for future use
c. A mechanism for code reuse in single inheritance languages
d. A special type of class
Answer: c. A mechanism for code reuse in single inheritance languages

4. In PHP, what is the purpose of the filter_var function with the FILTER_VALIDATE_EMAIL filter?
a. It checks if a variable is an email
b. It validates and sanitizes an email address
c. It filters out invalid email characters
d. It converts an email address to a lowercase
Answer: b. It validates and sanitizes an email address

5.What is the result of the expression echo strpos("Hello World", "W"); in PHP?
a. 0
b. 6
c. 5
d. False
Answer: b. 6

JavaScript Questions:

6. What is the purpose of the Object.freeze() method in JavaScript?
a. To create a new object
b. To prevent modifications to an object, such as adding or deleting properties
c. To deep clone an object
d. To merge two objects
Answer: b. To prevent modifications to an object, such as adding or deleting properties

7. What is the role of the async and await keywords in JavaScript?
a. To create asynchronous functions
b. To handle exceptions in synchronous code
c. To declare variables as asynchronous
d. To define synchronous functions
Answer: a. To create asynchronous functions

8. In JavaScript, what does this keyword refer to inside an arrow function?
a. It refers to the global object
b. It refers to the object that contains the arrow function
c. It is undefined
d. It refers to the calling object
Answer: b. It refers to the object that contains the arrow function

9. Which of the following is the correct way to remove an element from an array in JavaScript?
a. array.remove(index)
b. array.splice(index, 1)
c. array.pop(index)
d. array.trim(index)
Answer: b. array.splice(index, 1)

10. What is the purpose of the Promise.all() method in JavaScript?
a. To create a new Promise object
b. To handle rejected promises
c. To wait for all promises to resolve and return their results
d. To execute promises sequentially
Answer: c. To wait for all promises to resolve and return their results

11. What is the purpose of the declare(strict_types=1); statement in PHP?

a. To enforce strict type checking for all function parameters and return types

b. To declare a constant with the value 1

c. To enable strict error reporting

d. To define a global constant

Answer: a. To enforce strict type checking for all function parameters and return types

12. In PHP, what is the purpose of the array_column function?

a. To extract a single column from a multi-dimensional array

b. To merge multiple arrays into a single array

c. To sort an array based on its keys

d. To create a multi-dimensional array

Answer: a. To extract a single column from a multi-dimensional array

13. Which of the following statements is true about PHP's PDO (PHP Data Objects) extension?

a. PDO is used for parsing XML data

b. PDO is deprecated and should not be used in modern PHP applications

c. PDO provides a database access layer providing a uniform method of access to multiple databases

d. PDO is only compatible with MySQL databases

Answer: c. PDO provides a database access layer providing a uniform method of access to multiple databases

14. What is the purpose of the array_walk function in PHP?

a. To iterate over elements of an array and modify the array

b. To create a new array by applying a callback function to every element of an existing array

c. To sort an array in reverse order

d. To filter elements from an array based on a callback function

Answer: a. To iterate over elements of an array and modify the array

15. What does the Zend Engine refer to in the context of PHP?

a. A PHP extension for handling XML data

b. A template engine for PHP

c. The scripting engine that interprets PHP code

d. A built-in function for encrypting data

Answer: c. The scripting engine that interprets PHP code

JavaScript Questions:

16. What is the purpose of the localStorage object in JavaScript?

a. To store data in a database

b. To store data locally in the browser with no expiration time

c. To interact with server-side databases

d. To store cookies

Answer: b. To store data locally in the browser with no expiration time

17. Which of the following statements correctly describes the difference between null and undefined in JavaScript?

a. null represents an intentional absence of any object value, while undefined is assigned to a variable that has not been assigned a value

b. null represents an undefined value, while undefined represents a deliberate absence of value

c. null is a primitive data type, while undefined is an object

d. null and undefined are interchangeable and can be used interchangeably

Answer: a. null represents an intentional absence of any object value, while undefined is assigned to a variable that has not been assigned a value

18. What does the term "hoisting" refer to in the context of JavaScript?

a. The process of lifting heavy objects in a JavaScript program

b. The automatic moving of variable and function declarations to the top of their containing scope during the compilation phase

c. A technique for optimizing the performance of JavaScript code

d. The process of attaching event listeners to HTML elements

Answer: b. The automatic moving of variable and function declarations to the top of their containing scope during the compilation phase

19. Which of the following is used to create a new array with the results of calling a provided function on every element in the array in JavaScript?

a. map()

b. filter()

c. reduce()

d. forEach()

Answer: a. map()

20. What is the purpose of the super keyword in JavaScript?

a. To reference the parent class in a class hierarchy

b. To access the global object

c. To call a function with a specified value and arguments provided individually

d. To perform bitwise operations

Answer: a. To reference the parent class in a class hierarchy