Top questions with answers asked in MNC on PHP

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PHP interview questions along with their answers that might be asked in top multinational companies (MNCs):

  1. What is PHP, and what are its key features?
    • Answer: PHP (Hypertext Preprocessor) is a server-side scripting language widely used for web development. Its key features include:
      • Simplicity: PHP is easy to learn and use, with a syntax similar to C and Perl, making it accessible to beginners and experienced developers alike.
      • Flexibility: PHP can be embedded within HTML, allowing developers to mix dynamic content and server-side logic seamlessly within web pages.
      • Platform independence: PHP runs on various platforms, including Windows, macOS, Linux, and Unix, making it suitable for building cross-platform web applications.
      • Extensibility: PHP supports a wide range of extensions and libraries for additional functionality, such as database access, XML processing, image manipulation, and web services integration.
      • Performance: PHP offers good performance and scalability for web applications, with features like bytecode caching (e.g., OPcache) and asynchronous processing (e.g., Swoole) to improve speed and efficiency.
      • Community support: PHP has a large and active community of developers, contributors, and users who provide documentation, tutorials, forums, and third-party libraries, frameworks, and tools to support PHP development.
  2. What are the differences between PHP and other server-side scripting languages like Python and Ruby?
    • Answer: PHP, Python, and Ruby are all popular server-side scripting languages used for web development, but they differ in several key aspects:
      • Syntax: PHP has a syntax similar to C and Perl, with a focus on simplicity and ease of use. Python has a clean and readable syntax with significant whitespace indentation, while Ruby has a concise and expressive syntax inspired by Perl and Smalltalk.
      • Performance: PHP is optimized for web development and offers good performance and scalability for handling web requests. Python and Ruby are general-purpose programming languages with web frameworks (e.g., Django for Python, Ruby on Rails for Ruby) that provide higher-level abstractions and features but may have higher overhead and slower performance.
      • Ecosystem: PHP has a large ecosystem of extensions, libraries, and frameworks (e.g., Laravel, Symfony, CodeIgniter) for web development, with a focus on simplicity and ease of use. Python has a rich ecosystem of libraries and frameworks (e.g., Flask, Django) for web development, scientific computing, machine learning, and automation. Ruby has a mature ecosystem of libraries and frameworks (e.g., Ruby on Rails, Sinatra) for web development, with a focus on developer productivity and convention over configuration.
      • Community: PHP has a large and diverse community of developers, contributors, and users who provide documentation, tutorials, forums, and third-party resources. Python and Ruby also have vibrant communities with active development, support, and contributions to open-source projects.
  3. Explain the differences between include(), require(), include_once(), and require_once() in PHP.
    • Answer: include(), require(), include_once(), and require_once() are PHP functions used for including and evaluating external PHP files within a script, but they differ in their behavior when including files:
      • include(): The include() function includes and evaluates a specified PHP file in the current script. If the file cannot be included, include() generates a warning but continues execution of the script.
      • require(): The require() function includes and evaluates a specified PHP file in the current script. If the file cannot be included, require() generates a fatal error and halts execution of the script.
      • include_once(): The include_once() function behaves like include(), but it ensures that the specified file is included only once in the script, regardless of how many times include_once() is called.
      • require_once(): The require_once() function behaves like require(), but it ensures that the specified file is included only once in the script, regardless of how many times require_once() is called. In summary, include() and require() are used for including external PHP files, while include_once() and require_once() ensure that files are included only once to prevent duplicate declarations or definitions.
  4. What is the difference between GET and POST methods in PHP, and when would you use each?
    • Answer: GET and POST are two HTTP request methods used for sending data from a client (e.g., web browser) to a server (e.g., web server) in PHP and other web development languages:
      • GET method: GET requests are used for requesting data from a server and passing data in the URL query string. Data is appended to the URL as key-value pairs (e.g., example.com/page.php?key1=value1&key2=value2), making it visible in the browser’s address bar and limited in size. GET requests are idempotent, meaning they can be safely repeated without changing the server state, and they are typically used for retrieving data or performing read-only operations.
      • POST method: POST requests are used for submitting data to a server and passing data in the HTTP request body. Data is not visible in the URL and can be of larger size compared to GET requests. POST requests are not idempotent and can modify the server state, making them suitable for submitting form data, uploading files, or performing write operations. In general, use the GET method for retrieving data and performing read-only operations, and use the POST method for submitting data and performing write operations in PHP applications.
  5. How do you sanitize and validate user input in PHP to prevent security vulnerabilities like SQL injection and cross-site scripting (XSS)?
    • Answer: Sanitizing and validating user input is crucial for preventing security vulnerabilities in PHP applications. Some best practices for sanitizing and validating user input include:
      • Data validation: Validate user input against expected formats, data types, ranges, and constraints using functions like filter_var(), ctype_ functions, and regular expressions. Validate input on both the client and server sides to ensure data integrity and consistency.
      • Parameterized queries: Use parameterized queries (prepared statements) or parameter binding with PDO (PHP Data Objects) or MySQLi extensions to prevent SQL injection attacks by separating SQL logic from user input and automatically escaping special characters.
      • Output encoding: Encode output data using htmlspecialchars() or htmlentities() functions to prevent cross-site scripting (XSS) attacks by escaping HTML special characters and rendering user input as plain text in HTML documents.
      • Input filtering: Filter user input to remove or sanitize potentially dangerous characters, such as HTML tags, JavaScript code, SQL injection payloads, and other malicious content, using functions like filter_input(), filter_input_array(), and addslashes().
      • Content security policy: Implement a content security policy (CSP) to control the sources and types of content allowed to be loaded or executed in web pages, such as scripts, stylesheets, images, and fonts, to mitigate against XSS, data injection, and code execution attacks.