What are the most common PHP interview questions for freshers?

Common questions include: difference between echo and print, difference between GET and POST, session vs cookie, difference between == and ===, and explaining single vs double quotes.

What advanced PHP topics are asked in mid-level developer interviews?

Key topics include: PDO prepared statements vs MySQLi, PHP 8 JIT compiler, PSR standards (PSR-4 autoloading), Dependency Injection, Traits, and OOP Polymorphism.

How should university BCA students prepare for PHP practical viva exams?

Review syntax fundamentals, superglobals ($_GET, $_POST, $_SESSION), database CRUD code snippets, difference between include and require, and array functions.

Top 100+ PHP Interview Questions and Answers for BCA, CS Students & Job Seekers

Whether you are preparing for your university semester viva examination (BCA, BSc Computer Science, MCA, B.Tech) or getting ready for technical campus placement and web developer interviews, this comprehensive collection of 100+ Top PHP Questions and Answers covers all levels from core fundamentals to modern PHP 8 architecture.

Section 1: Core PHP Fundamentals (Freshers & BCA Viva)

Q1: What is PHP and what is its recursive acronym?

PHP stands for Hypertext Preprocessor. It is an open-source, server-side interpreted scripting language designed primarily for dynamic web development.

Q2: What is the difference between echo and print?

echo has no return value (void), can accept multiple comma-separated arguments, and is slightly faster. print always returns integer 1 and accepts only one argument. Both are language constructs.

Q3: Distinguish between == and === in PHP.

== (Equal) compares values after type coercion (e.g. 5 == "5" is true). === (Identical) checks that both value AND data type are strictly identical (e.g. 5 === "5" is false).

Q4: What is the difference between include and require?

If the target file is missing, include generates a warning and allows the script to continue. require generates a fatal compile error and halts script execution immediately.

Q5: What are Superglobals in PHP? Name at least five.

Superglobals are predefined associative arrays available automatically in all scopes without the global keyword. Examples: $_GET, $_POST, $_SESSION, $_COOKIE, $_SERVER, $_FILES, and $GLOBALS.

Section 2: Web Forms, Cookies & Sessions

Q6: Differentiate between Cookies and Sessions.

Cookies are stored on the client's browser (max ~4KB) and are accessible across requests. Sessions store application data securely on the web server; only a session identifier (PHPSESSID) is stored in the browser cookie.

Q7: How do you prevent Cross-Site Scripting (XSS) in form submissions?

Always sanitize user output using htmlspecialchars($input, ENT_QUOTES, 'UTF-8'). This safely encodes special characters like < and > into harmless HTML entities.

Q8: Why is session_start() required before any HTML output?

session_start() sets the session cookie in HTTP response headers. Outputting HTML or echo statements first sends headers prematurely, triggering "Headers already sent" errors.

Section 3: Databases & Security (MySQLi & PDO)

Q9: What is SQL Injection and how do Prepared Statements eliminate it?

SQL Injection occurs when user input is concatenated directly into SQL queries, altering command logic. Prepared statements pre-compile the SQL template on the database server; user inputs are bound purely as data parameters, making SQL injection impossible.

Q10: Why is PDO preferred over MySQLi in modern web applications?

PDO supports 12 different database engines (MySQL, PostgreSQL, SQLite, etc.) and named parameters (:param). MySQLi connects only to MySQL and supports only positional question mark (?) placeholders.