Top 30 Most Common Php Basic Interview Questions You Should Prepare For
Written by
James Miller, Career Coach
Stepping into a PHP development role, whether as a fresh graduate or an experienced developer transitioning technologies, often involves navigating the interview process. Technical interviews, especially for basic PHP roles, aim to gauge your foundational knowledge of the language, its core concepts, and how it's used in web development. Preparing for php basic interview questions is crucial to demonstrate your readiness and understanding of this ubiquitous server-side scripting language. Mastering the fundamentals not only helps you answer questions confidently but also builds a strong base for more complex topics. This article compiles 30 essential php basic interview questions, offering insights into why they are asked, how to approach your answer, and providing example responses to help you prepare effectively for your next interview.
What Are php basic interview questions?
php basic interview questions cover the core concepts and syntax of the PHP programming language. These questions are designed to assess a candidate's understanding of fundamental topics like variables, data types, operators, control structures (loops, conditionals), functions, arrays, string manipulation, and basic interaction with web concepts like forms, sessions, and cookies. For anyone applying for a junior PHP developer position or a role requiring foundational PHP knowledge, being proficient in these basic php interview questions is non-negotiable. They form the bedrock upon which more advanced topics like object-oriented programming (OOP), database interactions, framework usage, and security principles are built. A solid grasp of these basics is indicative of a candidate's potential for growth and ability to handle common web development tasks using PHP.
Why Do Interviewers Ask php basic interview questions?
Interviewers ask php basic interview questions for several key reasons. Firstly, they need to confirm that a candidate possesses the minimum required technical competence to perform the job. A strong understanding of the basics indicates that a candidate can write functional PHP code and understand existing codebases. Secondly, these questions reveal a candidate's problem-solving approach and logical thinking abilities within the context of the language. How a candidate explains a basic concept or solves a simple coding problem provides insight into their clarity of thought and communication skills. Lastly, while interviews might touch upon advanced topics, a firm grip on the basics is often seen as a predictor of success. Candidates who can articulate fundamental concepts clearly are typically better equipped to learn and adapt to more complex challenges. Demonstrating proficiency in php basic interview questions sets a positive tone and builds confidence with the interviewer.
Preview List
What is PHP?
Who is the father of PHP?
What are the common uses of PHP?
How do you redirect a page in PHP?
What is a session in PHP?
Explain the difference between static and dynamic websites.
What are variables in PHP?
Is PHP case-sensitive?
What does
echodo in PHP?What are the rules for determining the truth of any non-boolean value?
How can PHP and HTML interact?
What are predefined constants in PHP?
How do you write single and multi-line comments in PHP?
What is the purpose of
breakandcontinuestatements?What are arrays in PHP?
How does the
foreachloop work?Difference between indexed and associative arrays?
What are constructors and destructors?
Difference between
includeandrequire?What is
sessionstart()andsessiondestroy()?What are cookies in PHP?
What is PEAR in PHP?
What are some popular PHP frameworks?
Explain
GETandPOSTmethods.How do you create a new MySQL database using PHP?
What is the difference between
==and===operators?What is the use of the
finalkeyword?Explain error handling in PHP.
What are traits in PHP?
How do you set infinite script execution time?
1. What is PHP?
Why you might get asked this:
This is often the first question to gauge your basic understanding and definition of PHP. It confirms you know what the language is and its primary role.
How to answer:
Define PHP, mention its acronym's meaning, its primary use case (web development), and where it executes (server-side).
Example answer:
PHP stands for Hypertext Preprocessor. It's a widely-used open-source server-side scripting language specifically designed for web development. It can be embedded into HTML and is powerful for creating dynamic web content and interacting with databases.
2. Who is the father of PHP?
Why you might get asked this:
This tests your general knowledge about the history and origin of PHP, showing interest beyond just coding syntax.
How to answer:
State the name of the creator and the year it was initially released.
Example answer:
Rasmus Lerdorf is credited as the creator of PHP. He initially developed it in 1994.
3. What are the common uses of PHP?
Why you might get asked this:
This question assesses your awareness of PHP's practical applications in real-world web development scenarios.
How to answer:
List several common tasks or types of applications built using PHP, focusing on its server-side capabilities.
Example answer:
PHP is commonly used for generating dynamic page content, collecting form data, sending and receiving cookies, session management, database operations (CRUD), user authentication, and handling server-side file operations.
4. How do you redirect a page in PHP?
Why you might get asked this:
Redirecting is a fundamental web development task. This question checks if you know the standard PHP method for achieving it.
How to answer:
Explain the use of the header() function with the "Location" header. Mention it must be called before any output.
Example answer:
You redirect using the header() function with the Location: header. For example, header("Location: newpage.php");. It's critical to call this function before any output (like HTML or whitespace) is sent to the browser.
5. What is a session in PHP?
Why you might get asked this:
Sessions are crucial for maintaining state across multiple page requests, a common requirement in web applications.
How to answer:
Define a session as a way to store user information across different pages during a single visit. Explain its purpose in maintaining user state.
Example answer:
A session in PHP is a method used to store user information that can be accessed across multiple pages within a website during a single visit. It allows you to preserve data like login status, shopping cart items, or user preferences.
6. Explain the difference between static and dynamic websites.
Why you might get asked this:
This question tests your understanding of the fundamental distinction between client-side and server-side processing in web pages, setting the stage for PHP's role.
How to answer:
Describe static sites as having fixed content served directly, and dynamic sites as generating content on-the-fly, often using server-side scripting like PHP and databases.
Example answer:
Static websites serve pre-built, fixed content (usually HTML files) that look the same for all users. Dynamic websites generate content based on user interactions, time, or data from a database using server-side scripting like PHP, making pages personalized or interactive.
7. What are variables in PHP?
Why you might get asked this:
Understanding variables is fundamental to any programming language. This verifies your knowledge of PHP's specific syntax and usage.
How to answer:
Define variables, explain their purpose (storing data), and describe the PHP syntax for declaring them (the $ sign).
Example answer:
Variables in PHP are used to store pieces of data. They start with a dollar sign ($) followed by the variable name. PHP is loosely typed, meaning you don't need to declare the data type explicitly; it's determined at runtime.
8. Is PHP case-sensitive?
Why you might get asked this:
This checks your attention to detail regarding PHP's syntax rules, particularly for variable and function names.
How to answer:
Specify exactly which parts of PHP are case-sensitive (variables) and which are not (function names, keywords).
Example answer:
Yes, PHP is partially case-sensitive. Variable names are case-sensitive (e.g., $name is different from $Name). However, function names, class names, and keywords (like if, echo, while) are not case-sensitive.
9. What does echo do in PHP?
Why you might get asked this:
echo is one of the most basic output constructs. This confirms you know how to display information to the browser using PHP.
How to answer:
Explain that echo is used to output strings or variables. Mention it's a language construct, not a function.
Example answer:
echo is a language construct in PHP used to output data to the browser. It's primarily used for displaying strings, numbers, or variable values. Unlike print, it can output multiple strings (separated by commas) and is slightly faster.
10. What are the rules for determining the truth of any non-boolean value?
Why you might get asked this:
This tests your understanding of type juggling and truthiness in PHP, which is important for conditional logic.
How to answer:
Explain PHP's loose typing and list common values that evaluate to false in a boolean context.
Example answer:
In PHP's loose typing, several non-boolean values evaluate to false in a boolean context. These include integers 0, float 0.0, the empty string "", the string "0", an empty array [], the special value NULL, and objects with no elements if treated as arrays.
11. How can PHP and HTML interact?
Why you might get asked this:
PHP's primary use is in web development, so understanding its interaction with HTML is fundamental.
How to answer:
Explain that PHP code can be embedded within HTML using special tags and that PHP can also generate HTML dynamically.
Example answer:
PHP and HTML interact by embedding PHP code within HTML files using tags. The server processes the PHP code before sending the page to the browser, allowing PHP to generate HTML content dynamically based on logic or data.
12. What are predefined constants in PHP?
Why you might get asked this:
Predefined constants are useful for getting runtime information. Knowing them shows a deeper understanding of built-in PHP features.
How to answer:
Define predefined constants and give a couple of examples, explaining their purpose.
Example answer:
Predefined constants are special constants provided by PHP that give information about the environment, script execution, or the PHP version. Examples include LINE (current line number), FILE (full path and filename), and PHP_VERSION.
13. How do you write single and multi-line comments in PHP?
Why you might get asked this:
Comments are essential for code readability and maintenance. This checks your knowledge of basic documentation practices.
How to answer:
Provide the syntax for both single-line and multi-line comments.
Example answer:
In PHP, you use // for single-line comments. For multi-line comments, you use / ... /. Comments are ignored by the PHP parser and are only for human readers.
14. What is the purpose of break and continue statements?
Why you might get asked this:
These control flow statements are common in loops. This tests your understanding of how to alter loop execution.
How to answer:
Explain what break does (exits loop/switch) and what continue does (skips current iteration).
Example answer:
The break statement is used to exit prematurely from a loop (like for, while, do-while, foreach) or a switch statement. The continue statement is used inside loops to skip the rest of the current iteration and proceed to the next one.
15. What are arrays in PHP?
Why you might get asked this:
Arrays are fundamental data structures used frequently in PHP for storing collections of data.
How to answer:
Define an array as a variable holding multiple values. Mention the different types of arrays in PHP (indexed, associative, multidimensional).
Example answer:
An array in PHP is a special variable that can hold more than one value at a time. PHP supports indexed arrays (using numeric keys), associative arrays (using named keys), and multidimensional arrays (arrays containing other arrays).
16. How does the foreach loop work?
Why you might get asked this:
The foreach loop is specifically designed for iterating over arrays and is commonly used.
How to answer:
Explain its purpose (iterating over arrays) and describe the syntax and how it accesses elements (value only or key-value pairs).
Example answer:
The foreach loop is used to iterate over elements of an array. It provides an easy way to loop through each item. It can work with just the value (foreach ($array as $value)) or with both the key and value (foreach ($array as $key => $value)).
17. Difference between indexed and associative arrays?
Why you might get asked this:
This tests your understanding of the different ways data can be keyed and accessed within PHP arrays.
How to answer:
Clearly state that indexed arrays use integer keys (starting from 0 by default) and associative arrays use named or string keys.
Example answer:
Indexed arrays in PHP use integers as keys to access elements, typically starting from 0. Associative arrays use named keys, which are usually strings, allowing you to access elements using descriptive names instead of numbers.
18. What are constructors and destructors?
Why you might get asked this:
This delves into basic Object-Oriented Programming (OOP) concepts in PHP, relevant even for basic roles.
How to answer:
Define what each method does within a class context (construct initializes objects, destruct cleans up).
Example answer:
In PHP classes, the constructor (construct()) is a special method that is automatically called when you create a new object of that class. It's used for initializing the object's properties. The destructor (destruct()) is called when an object is no longer referenced or explicitly destroyed, typically for cleanup tasks.
19. Difference between include and require?
Why you might get asked this:
Both are used for file inclusion, but their error handling differs significantly. This tests your understanding of robust coding practices.
How to answer:
Explain that both include files, but differentiate their behavior when the file is not found (include issues a warning, require causes a fatal error).
Example answer:
Both include and require are used to include code from another file into the current script. The main difference is error handling: include will only produce a warning if the file is not found and the script continues execution, while require produces a fatal error and halts script execution.
20. What is sessionstart() and sessiondestroy()?
Why you might get asked this:
These are the core functions for managing sessions, a key aspect of maintaining state in web applications.
How to answer:
Explain the purpose of each function in managing PHP sessions.
Example answer:
sessionstart() is used to initialize a session or resume an existing one. It must be called before accessing any session variables. sessiondestroy() is used to end a session. It removes all session data stored on the server for that specific session ID.
21. What are cookies in PHP?
Why you might get asked this:
Cookies are another fundamental mechanism for maintaining state and remembering users across visits.
How to answer:
Define cookies, explain where they are stored (client browser), and mention their use (remembering users, tracking).
Example answer:
Cookies are small pieces of data stored on the client's browser by a website. PHP can set and retrieve cookie values using functions like setcookie(). They are typically used to remember users, store preferences, or track user behavior across visits.
22. What is PEAR in PHP?
Why you might get asked this:
This tests your knowledge of the PHP ecosystem and common ways to distribute and use reusable code.
How to answer:
Explain that PEAR is a framework and distribution system for reusable PHP components, essentially a code repository.
Example answer:
PEAR stands for PHP Extension and Application Repository. It's a framework and distribution system for reusable PHP components, providing a structured library of code for common functions and tasks that developers can install and use in their projects.
23. What are some popular PHP frameworks?
Why you might get asked this:
This assesses your awareness of modern PHP development practices and tools that improve efficiency and structure.
How to answer:
List a few well-known PHP frameworks. Mention their purpose (providing structure, speeding development).
Example answer:
Popular PHP frameworks include Laravel, Symfony, CodeIgniter, and CakePHP. Frameworks provide a structured codebase and libraries for common tasks, helping developers build web applications faster and more maintainably following best practices.
24. Explain GET and POST methods.
Why you might get asked this:
These are the most common HTTP methods used in forms and requests. Understanding their difference is crucial for handling web input securely.
How to answer:
Describe how data is sent with each method, their visibility, limitations, and typical use cases (GET for retrieval, POST for submission).
Example answer:
GET and POST are HTTP methods for sending data. GET appends data to the URL (visible, limited data size), typically for requesting data. POST sends data in the HTTP request body (not visible in URL, larger data size capacity), typically for submitting data like form input or file uploads.
25. How do you create a new MySQL database using PHP?
Why you might get asked this:
Basic database interaction is fundamental for many PHP roles. This tests your ability to execute SQL commands via PHP.
How to answer:
Outline the steps: connect to the database server, formulate the SQL CREATE DATABASE query, and execute it using appropriate PHP database functions (e.g., mysqli_query).
Example answer:
To create a database using PHP and MySQL, you first establish a connection to the MySQL server (without specifying a database initially). Then, you write the SQL query CREATE DATABASE databasename; as a string. Finally, you execute this query using a function like mysqliquery() or PDO's exec() method.
26. What is the difference between == and === operators?
Why you might get asked this:
This is a classic question testing your understanding of PHP's type juggling and strict comparison.
How to answer:
Explain that == performs loose comparison (value after type coercion), while === performs strict comparison (value and type must match).
Example answer:
The == operator performs a loose comparison, meaning it checks if two values are equal after potentially converting one or both to a common type. The === operator performs a strict comparison, checking if two values are equal AND of the same data type without type conversion.
27. What is the use of the final keyword?
Why you might get asked this:
This tests your knowledge of OOP principles related to inheritance and preventing modification.
How to answer:
Explain that the final keyword prevents inheritance when applied to a class, and prevents overriding when applied to a method within a class.
Example answer:
The final keyword in PHP is used to prevent inheritance or method overriding. If you declare a class as final, it cannot be extended by other classes. If you declare a method within a class as final, it cannot be overridden by child classes.
28. Explain error handling in PHP.
Why you might get asked this:
Knowing how to handle errors is crucial for writing robust applications.
How to answer:
Mention PHP's error reporting levels, built-in error handling functions, and modern techniques like exceptions and try-catch blocks.
Example answer:
PHP has various error reporting levels (notices, warnings, fatal errors). Error handling can be managed using built-in functions like errorreporting(), seterror_handler(), or using exceptions with try...catch blocks, which is the preferred method for handling expected errors gracefully in modern PHP.
29. What are traits in PHP?
Why you might get asked this:
Traits were introduced later in PHP to help with code reuse in a single inheritance model. This tests awareness of more recent language features.
How to answer:
Define traits as a mechanism for code reuse, allowing methods from traits to be included in multiple classes, helping overcome limitations of single inheritance.
Example answer:
Traits are a mechanism for code reuse in single inheritance languages like PHP. A trait is a collection of methods that can be injected into classes. They allow a class to inherit methods from multiple traits, providing a way to share code between otherwise unrelated classes.
30. How do you set infinite script execution time?
Why you might get asked this:
Occasionally, long-running scripts are necessary. This tests your knowledge of controlling script execution limits.
How to answer:
Provide the function used to set the maximum execution time and the specific value for infinite execution.
Example answer:
You can set infinite script execution time using the settimelimit() function. Calling settimelimit(0); within your script will remove the maximum execution time limit imposed by PHP configuration.
Other Tips to Prepare for a php basic interview questions
Mastering the php basic interview questions listed above is a significant step, but effective preparation extends beyond just memorizing answers. Practice writing code for small problems that utilize these concepts. Try implementing simple forms that use GET/POST, managing sessions, or interacting with arrays. As Bjarne Stroustrup, the creator of C++, wisely said, "Our most important tool as programmers is our ability to handle complexity." Understanding basic PHP building blocks helps manage the complexity of larger applications.
Consider practicing explaining concepts out loud. Can you describe sessions or the difference between include and require clearly and concisely without referring to notes? Simulating interview scenarios can be incredibly beneficial. Utilizing tools like the Verve AI Interview Copilot (available at https://vervecopilot.com) can provide realistic practice environments and AI-powered feedback, helping you refine your responses to common php basic interview questions and technical challenges. Don't hesitate to revisit documentation for clarity on specific functions or syntax. As the famous programming quote goes, "Good programmers use documentation." Familiarity with the PHP manual will give you confidence. Preparing with a mix of theoretical knowledge, practical coding, and simulated practice runs, perhaps with a tool like Verve AI Interview Copilot, will significantly boost your readiness for any php basic interview questions.
Frequently Asked Questions
Q1: How long should my answers to php basic interview questions be?
A1: Aim for clear, concise answers, typically 2-4 sentences, directly addressing the question without excessive jargon.
Q2: Should I write code during a basic PHP interview?
A2: Often yes. Be prepared to write simple code snippets for tasks like array manipulation, string functions, or basic control flow.
Q3: Are frameworks like Laravel considered basic PHP?
A3: Frameworks are built using PHP, but knowledge of a specific framework is usually considered beyond basic PHP fundamentals.
Q4: What's the most important basic concept to know?
A4: Understanding variables, data types, control structures, and how PHP interacts with HTML/HTTP requests (GET/POST) is fundamental.
Q5: How can I practice for php basic interview questions?
A5: Practice writing code, explain concepts to others, and use online resources like tutorials and interview preparation tools.
Q6: Is knowing basic SQL required for PHP interviews?
A6: Often, yes. Basic database interaction is common in PHP development, so understanding SQL basics is highly recommended.
