100+ PHP Developer Interview Questions and Answers

Errors can be reported in log files using error_log() function in PHP.

• Use error_log() function to log errors in a file

• Specify the error message and the log file path as parameters

• Example: error_log('Error message', 3, '/var/log/php_errors.log')

• Use error_reporting() function to set the level of error reporting

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

• Syntax errors occur when the code violates the rules of PHP syntax.

• Runtime errors occur during the execution of the script, such as division by zero or accessing undefined variables.

• Logical errors do not cause the script to terminate, but they produce incorrect results or unexpected behavior.

Rotate array elements based on number of loops specified.

• Create a new array by slicing the original array based on the number of loops specified.

• Concatenate the sliced array with the remaining elements of the original array.

• Handle edge cases where the number of loops is greater than the array length by using modulo operator.

Query to get 4th highest salary from employees table

• Use ORDER BY and LIMIT to get the 4th highest salary

• Join the employees table with itself to avoid duplicates

• Use subquery to get the 4th highest salary

PHP has over 100 array functions and over 200 string functions.

• Array functions include: array_push(), array_pop(), array_merge(), array_slice(), etc.

• String functions include: strlen(), str_replace(), substr(), strtolower(), etc.

• PHP also has functions for working with regular expressions, dates, and more.

• The exact number of functions may vary depending on the version of PHP being used.

Yes, I have experience implementing shipping APIs in previous projects.

• I have integrated shipping APIs in e-commerce websites to automate shipping calculations and tracking.

• I have used shipping APIs from providers like UPS, FedEx, and USPS to provide accurate shipping rates to customers.

• I have customized shipping API implementations to suit the specific needs of the project, such as handling international shipping or special delivery options.

Implementing a hotel booking system like Oyo in PHP

• Use PHP frameworks like Laravel or CodeIgniter for efficient development

• Implement user authentication and authorization for secure access

• Create a database schema to store hotel details, room availability, and bookings

• Develop a user-friendly interface for searching and booking hotels

• Incorporate payment gateway integration for online transactions

DBMS is a software system that manages databases, RDBMS is a type of DBMS that stores data in a structured format, ODBMS is a type of DBMS that stores data in an object-oriented manner.

• DBMS (Database Management System) is a software system that allows users to interact with a database. Examples include MySQL, Oracle, SQL Server.

• RDBMS (Relational Database Management System) is a type of DBMS that stores data in tables with rows and columns. Examples include MySQL, PostgreSQL, ...read more

Echo and print are both used to output data in PHP, but echo is slightly faster and can take multiple arguments.

• Echo is a language construct, while print is a function.

• Echo does not return a value, while print returns 1.

• Echo can output multiple strings separated by commas, while print can only output one string.

• Echo is generally preferred for performance reasons.

MVC is a software design pattern that separates an application into three interconnected components: Model, View, and Controller.

• Model represents the data and business logic of the application.

• View is responsible for rendering the user interface.

• Controller handles user input and updates the model and view accordingly.

• Library is a collection of pre-written code that can be reused in different projects.

• Helper function is a function that performs a specific task and can be calle...read more

Middleware in Laravel is a mechanism that allows filtering HTTP requests entering your application.

• Middleware can be used to authenticate users, authorize access, handle CORS, log requests, etc.

• Middleware can be applied globally to all routes or specific to certain routes or groups of routes.

• To create a middleware, use the `make:middleware` Artisan command.

• Middleware can be registered in the `app/Http/Kernel.php` file.

• Middleware can be assigned to routes using the `middleware...read more

Use a MySQL query to select data with employee name, code, and their manager using manager_id as foreign key.

• Use JOIN to connect the employee and manager tables based on the manager_id foreign key

• Select the employee name, code, and manager's name using appropriate aliases

• Make sure to specify the table names and columns correctly in the query

Questions related to PHP development including cookies, sessions, CSS, database connection, and form design.

• Cookies are small text files stored on the client-side to remember user information.

• Sessions are server-side data storage to maintain user information across multiple pages.

• CSS can be used to style HTML elements side by side using the display property.

• To retrieve a column from a database using PHP, use the SELECT statement in SQL.

• While loop is used in PHP for repetitive...read more

Multiple inheritance allows a class to inherit from multiple parent classes, while multilevel inheritance involves a chain of inheritance.

• Multiple inheritance allows a class to inherit from more than one parent class.

• Multilevel inheritance involves a chain of inheritance, where a class inherits from another class, which in turn inherits from another class.

• In multiple inheritance, a class can inherit attributes and methods from multiple parent classes.

• In multilevel inheritance...read more

Closures are anonymous functions that can be assigned to a variable and used as a callback function.

• Closures are used to create functions that can be passed as arguments to other functions.

• They can access variables outside of their scope, making them useful for creating flexible and reusable code.

• Closures are often used in event handling, asynchronous programming, and functional programming.

• Example: $add = function($a, $b) { return $a + $b; };

• Example: usort($array, function($...read more

Answers to common PHP developer interview questions

• Session is a way to store user data on the server side

• Triggers are used to execute a set of SQL statements when a specific event occurs

• Views are virtual tables that display data from one or more tables

• Array functions include array_push, array_pop, array_merge, and more

• GET and POST are HTTP methods used to send data to a server

• Abstract classes cannot be instantiated and are used as templates for other classes

• Function overloadi...read more

The output of a PHP program using And and Or depends on the logic used in the program.

• And (&&) returns true if both conditions are true

• Or (||) returns true if at least one condition is true

• The output will depend on the logic used in the program

array_merge merges two or more arrays into one, while array_combine creates an array by using one array for keys and another for its values.

• array_merge combines the values of two or more arrays into a single array

• array_combine creates an array using one array for keys and another for its values

• array_merge preserves numeric keys, while array_combine uses the first array for keys and the second for values

• array_merge can merge arrays with non-numeric keys, while array_combine re...read more

Cookies store data on client-side while sessions store data on server-side.

• Cookies are vulnerable to cross-site scripting (XSS) attacks while sessions are not.

• Cookies can be tampered with by the client while sessions cannot.

• Sessions are more secure as they do not expose sensitive data to the client.

• Cookies have an expiration time while sessions expire when the user closes the browser.

• Sessions are preferred for sensitive data while cookies are preferred for non-sensitive data.

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

• Syntax errors occur when there is a mistake in the code that prevents it from being parsed correctly by the PHP engine. For example, missing semicolons or parentheses.

• Runtime errors occur during the execution of the code, such as division by zero or calling a function that does not exist.

• Logical errors occur when the code runs without any syntax or runtime errors, but does not produ...read more

Laravel follows a series of steps to handle a request and generate a response.

• The request is first received by the web server and passed to the index.php file in the public directory.

• The index.php file loads the Laravel framework and creates an instance of the application.

• The application then handles the request by routing it to the appropriate controller method.

• The controller method processes the request and returns a response.

• The response is then sent back to the web server...read more

Ajax is a technique used to update parts of a web page without reloading the entire page. It stands for Asynchronous JavaScript and XML.

• Ajax allows for asynchronous communication between the client and server.

• It uses JavaScript to send and receive data from the server without interfering with the display and behavior of the existing page.

• Ajax can be used to dynamically update content, submit forms without refreshing the page, and fetch data from the server.

• It typically uses X...read more

Query to find count of duplicate records in MySQL

• Use GROUP BY clause to group the records by the column(s) that may have duplicates

• Use HAVING clause to filter out the groups with count less than 2

• Use COUNT() function to count the number of records in each group

SQL injection is a type of cyber attack where malicious SQL statements are inserted into an entry field to manipulate the database.

• SQL injection is a common attack on web applications that use SQL databases.

• Attackers can use SQL injection to bypass authentication, steal data, or modify data.

• SQL injection can be prevented by using prepared statements, input validation, and limiting database privileges.

• Example: If a login form is vulnerable to SQL injection, an attacker can ent...read more

Padding is the space inside an element, while margin is the space outside an element.

• Padding is the space between the content and the border of an element

• Margin is the space outside the border of an element

• Padding affects the size of the element itself, while margin affects the spacing between elements

• Example:

  Content

include() includes a file multiple times while include_once() includes it only once.

• include() can include the same file multiple times, causing errors

• include_once() checks if the file has already been included and skips it if so

• include() is faster than include_once() but can cause issues with redeclaring functions or classes

CodeIgniter follows the Model-View-Controller (MVC) architectural pattern.

• The request is first routed to the controller

• The controller loads the model and fetches data from the database

• The controller then loads the view and passes the data to it

• The view is then rendered and displayed to the user

PHP is a server-side scripting language used for web development. Data can be sent from frontend to backend using forms or AJAX.

• Use HTML forms to send data to backend PHP scripts

• Use AJAX to send data asynchronously to backend PHP scripts

• Data can be sent via GET or POST methods

PHP is a server-side scripting language used for web development. Echo and print are used to output data. Server-side handles requests.

• PHP is a popular language for web development

• Echo and print are used to output data to the browser

• Server-side refers to the processing of requests on the server

• Client-side refers to the processing of requests on the user's browser

Arrays and string functions are essential in PHP development.

• Array functions: array_push(), array_pop(), array_merge(), array_slice()

• String functions: strlen(), str_replace(), strpos(), strtolower()

• Examples: array_push($array, 'value'), strlen('hello'), str_replace('world', 'PHP', 'Hello world')

I follow PSR coding standards and adhere to best practices.

• I follow PSR-1 and PSR-2 coding standards.

• I use meaningful variable and function names.

• I write clean and readable code.

• I use proper indentation and spacing.

• I avoid using global variables.

• I use comments to explain complex code.

• I adhere to best practices for security and performance.

• For example, I always use prepared statements to prevent SQL injection attacks.

Multiple inheritance cannot be achieved directly in PHP, as it only supports single inheritance.

• PHP does not support multiple inheritance, where a class can inherit from multiple parent classes.

• However, PHP supports a form of multiple inheritance through interfaces.

• Interfaces allow a class to inherit from multiple interfaces, providing a way to achieve multiple inheritance-like behavior.

• By implementing multiple interfaces, a class can inherit and implement the methods defined...read more

My approach to building basic logic skills involves practicing problem-solving exercises, breaking down complex problems into smaller parts, and seeking feedback to improve.

• Practice problem-solving exercises regularly to strengthen logical thinking abilities.

• Break down complex problems into smaller, more manageable parts to better understand the problem and find solutions.

• Seek feedback from peers or mentors to identify areas for improvement and refine logic skills.

• Utilize res...read more

Yes, I am comfortable switching between multiple technologies.

• I have experience working with multiple technologies such as PHP, Python, and Java.

• I am adaptable and can quickly learn new technologies as needed.

• Switching between technologies is a common requirement in software development.

• I am comfortable working with both front-end and back-end technologies.

I have worked on PHP 5 and PHP 7.

• I have experience working with PHP 5 and PHP 7.

• I have developed web applications using PHP 5 and PHP 7.

• I am familiar with the differences between PHP 5 and PHP 7, such as improved performance and new features.

• I have used PHP 7's type declarations and return type declarations in my code.

• I have also worked with PHP frameworks such as Laravel and CodeIgniter.

Object-oriented concepts are fundamental principles in programming that allow for the creation and manipulation of objects.

• Encapsulation: bundling data and methods together in a single unit (class)

• Inheritance: creating new classes from existing ones, inheriting their properties and behaviors

• Polymorphism: the ability of objects to take on many forms, allowing for flexibility and extensibility

• Abstraction: simplifying complex systems by breaking them down into smaller, more mana...read more

The query to get the employee with the 3rd maximum salary in MySQL.

• Use the ORDER BY clause to sort the salaries in descending order.

• Use the LIMIT clause to retrieve the third row.

• Use a subquery to select the third maximum salary.

Magic methods in PHP are special methods that are automatically called in response to certain events or actions.

• Magic methods start with a double underscore (__) followed by the method name.

• They are used to implement functionality such as overloading, property access, and object serialization.

• Examples of magic methods include __construct(), __get(), __set(), __toString(), etc.

Indexing is the process of creating an index for faster data retrieval. DOM can be loaded without refreshing the page using AJAX.

• Indexing involves creating a data structure that allows for faster searching and retrieval of data.

• It works by creating a separate index file that contains pointers to the actual data.

• Loading data in DOM without refreshing the page can be achieved using AJAX (Asynchronous JavaScript and XML).

• AJAX allows for sending and receiving data from the server...read more

MySQL has multiple storage engines including InnoDB, MyISAM, and more.

• MySQL has a pluggable storage engine architecture

• InnoDB is the default storage engine for MySQL

• MyISAM is another popular storage engine

• Other storage engines include Memory, CSV, and more

MyISAM is faster but doesn't support transactions, while InnoDB is slower but supports transactions and foreign keys.

• MyISAM is the default storage engine for MySQL, while InnoDB is an alternative.

• MyISAM is faster for read-heavy applications, while InnoDB is better for write-heavy applications.

• MyISAM doesn't support transactions or foreign keys, while InnoDB does.

• MyISAM uses table-level locking, while InnoDB uses row-level locking.

• MyISAM is more suitable for small to medium-si...read more

Char is a fixed-length data type while varchar is a variable-length data type.

• Char is used for storing fixed-length strings while varchar is used for storing variable-length strings.

• Char takes up more space than varchar as it reserves space for the maximum length of the string.

• Varchar is more flexible than char as it can store strings of varying lengths.

• Char is faster than varchar for fixed-length strings as it does not require any additional checks for length.

The interview questions cover PHP array functions, form validation in CodeIgniter, MySQL joins query, MVC structure of CI, and Rest APIs.

• PHP array functions: Use functions like array_push, array_pop, array_merge, etc. to manipulate arrays in PHP.

• Form validation in CodeIgniter: Use CodeIgniter's form validation library to validate user input in forms.

• MySQL joins query: Use JOIN clauses in SQL queries to combine rows from two or more tables based on a related column between the...read more

HTML is a markup language used for creating web pages. Python is a high-level programming language used for various applications.

• HTML stands for Hypertext Markup Language

• It is used for creating the structure and content of web pages

• Python is an interpreted language with dynamic semantics

• It is used for web development, data analysis, artificial intelligence, etc.

• Python uses indentation for block statements instead of curly braces

Abstract classes and interfaces are used to define common methods and properties for classes to implement.

• Abstract classes cannot be instantiated and can contain both abstract and non-abstract methods.

• Interfaces only contain method signatures and constants, and classes can implement multiple interfaces.

• Abstract classes are useful for creating a base class with common functionality, while interfaces are useful for defining a contract for classes to follow.

• Example: abstract cla...read more

Exceptions can be handled using try-catch blocks in PHP.

• Use try-catch blocks to enclose the code that may throw an exception.

• Catch the exception using catch block and handle it appropriately.

• Multiple catch blocks can be used to handle different types of exceptions.

• Finally block can be used to execute code regardless of whether an exception occurred or not.

include() includes and evaluates a specified file, while include_once() does the same but ensures the file is only included once.

• include() can include the same file multiple times, while include_once() will only include it once

• include() will continue to execute the script even if the file is not found, while include_once() will throw a warning and continue

• include_once() is useful for preventing multiple declarations of functions or classes