Nowfloats Technologies Front end Developer Interview Questions and Answers for Experienced

Find pair of elements in an array whose sum is equal to a given number K.

• Iterate through the array and for each element, check if K minus the element exists in the array.

• Use a hash table to store the elements and their indices for faster lookup.

• If multiple pairs exist, return any one of them.

• If no pair exists, return null or an appropriate message.

Session is maintained using session affinity or sticky sessions.

• Session affinity ensures that a user's session is always directed to the same server.

• Load balancer uses a unique identifier to route requests to the same server.

• Sticky sessions can be implemented using cookies or URL rewriting.

• Session replication can also be used to maintain session data across multiple servers.

Singleton pattern ensures only one instance of a class is created and provides a global point of access to it.

• Create a private constructor to prevent direct instantiation of the class

• Create a private static instance of the class

• Create a public static method to access the instance

• Ensure thread safety by using synchronized keyword or static initialization block

• Examples: Logger, Configuration Manager, Database Connection

Explaining abstract class, interface and multiple inheritance in PHP.

• Abstract class is a class that cannot be instantiated and can have abstract methods.

• Interface is a collection of abstract methods and constants that can be implemented by a class.

• Multiple inheritance is not possible in PHP, but can be achieved using interfaces.

• Interfaces can be implemented by multiple classes, allowing for multiple inheritance-like be

Write a stored procedure from given tables and conditions

• Identify the tables and their relationships

• Determine the conditions to be used in the stored procedure

• Write the SQL code for the stored procedure

• Test the stored procedure to ensure it returns the desired results

To increase PHP memory at run time, modify the php.ini file or use ini_set() function.

• Edit the memory_limit value in php.ini file

• Use ini_set('memory_limit', '256M') function to increase memory limit at run time

• Check for memory leaks in the code

• Use unset() function to free up memory after use

php.ini is a configuration file for PHP that allows users to customize various settings.

• Change PHP settings such as memory limit, file upload size, and error reporting

• Enable or disable extensions and modules

• Set timezone and language settings

• Configure email settings

• Control caching and session settings

Use window.location to get domain from a url in jQuery.

• Use window.location to get the full url

• Use .hostname to get the domain name

• Use .replace() to remove 'www.' if present

WAP to find smallest palindrome number larger than given number.

• Convert the given number to string and check if it is already a palindrome.

• If not, increment the number and check if it is a palindrome.

• Repeat until a palindrome number larger than the given number is found.

• Use a while loop to implement the above steps.

WAP to check if linked list elements is a palindrome without using any extra space.

• Traverse the linked list and reverse the second half of the list

• Compare the first half with the reversed second half

• Use two pointers to traverse the list, one at normal speed and other at double speed

Find the first non-repeating character in a string.

• Create a hash table to store the frequency of each character in the string.

• Iterate through the string and check the frequency of each character.

• Return the first character with a frequency of 1.

Connection pooling is a technique of reusing database connections to improve performance.

• Connection pooling helps to reduce the overhead of creating and destroying database connections.

• It maintains a pool of connections that can be reused by multiple clients.

• Connection pooling is commonly used in web applications to handle multiple requests simultaneously.

• It can be configured with parameters like maximum number of conn...read more

A singleton class in PHP is a class that can only be instantiated once.

• Create a private constructor to prevent direct instantiation

• Create a private static variable to hold the instance of the class

• Create a public static method to get the instance of the class

• Ensure that the public static method always returns the same instance

To connect to MySQL database using PHP, create a Connection class.

• Use mysqli_connect() function to establish a connection

• Pass the database credentials as parameters to the function

• Create a constructor method to initialize the connection

• Create a query method to execute SQL queries

• Close the connection using mysqli_close() method

There are three types of errors in PHP: syntax errors, runtime errors, and logical errors.

• Syntax errors occur when the code is not written correctly, such as missing semicolons or parentheses.

• Runtime errors occur during the execution of the code, such as trying to access an undefined variable.

• Logical errors occur when the code runs without errors, but produces unexpected results, such as a miscalculation in a formula.

Session in PHP allows to store user data on the server for later use.

• Session starts when a user logs in and ends when the user logs out or the session expires.

• Session data is stored on the server and identified by a unique session ID.

• Session variables can be set and accessed using the $_SESSION superglobal array.

• Session can be destroyed using the session_destroy() function.

• Session can be used to store user-specific dat...read more

Find missing element in an array of elements from 0 to n-1

• Calculate sum of all elements in array and subtract from sum of n natural numbers

• Use XOR operation on all elements and n natural numbers

• Sort the array and find the missing element