PHP Interview Questions

What is PHP?

• PHP is a server side scripting language that is open-source and widly used in web development.Many database are supported, including mysql, Orcale, Sybase, Solid Postgre SQL.

What Exactly Pear in PHP?

• PEAR is a PHP framework and repository that contains reusable PHP components.
• PEAR is an acronym that stands for PHP Extension and application repository.
• It includes a wide range of PHP code snippets and libraries.

Explain the difference between Static and Dynamic Website?

• The main difference between static and dynamic websites lies in how the content is generated and delivered to the user.

Static Websites:

Dynamic Websites:

• Dynamic websites generate content on the fly, allowing for personalized and interactive experiences.
• The content of a dynamic website is often stored in a database or fetched from external sources.
• Dynamic websites use technologies such as server-side scripting languages (e.g., PHP, Python, Ruby) or content management systems (CMS) to retrieve data, process it, and generate HTML dynamically.
• The same dynamic web page can display different content based on various factors like user input, user preferences, or database queries.
• Dynamic websites are suitable for applications that require frequent updates, user interactions (e.g., user registration, commenting systems), and content that changes dynamically.
• Examples of dynamic websites include e-commerce platforms, social media networks, and online banking systems.
• In summary, static websites have fixed content that doesn’t change unless manually updated, while dynamic websites generate content on the fly using server-side scripting or CMS, allowing for interactive and personalized experiences.

What is PHP Session? (Click For Detail)

• A session is a way to store information that will be widly used accross multiple pages of a websites.
• The session will create a file in a temprory directory on the server to store registered session variables and their values.

What is difference between $message and $$message?

• In PHP, the difference between $message and $$message lies in the way they are used for variable naming and variable variables.

$message:

• $message is a regular variable that is assigned a specific value.
• It follows the standard variable naming convention in PHP, where the variable name starts with a dollar sign ($) followed by a valid variable name.
• The value assigned to $message can be accessed using $message.

What is difference between echo and print?

• In PHP, both echo and print are used to output strings or variables to the browser or the output stream. However, there are a few differences between them:

Return Value:

• echo does not have a return value. It is a language construct rather than a function.
• print is a language construct as well but behaves like a function. It returns a value of 1, which can be used in expressions.

Syntax:

• echo can accept multiple arguments and does not require parentheses. It can be used with or without parentheses, but the parentheses are generally omitted.
• Example: echo “Hello”, “World”; or echo(“Hello World”);
• print can only accept a single argument and requires parentheses.
• Example: print(“Hello World”);

Usability:

• echo is slightly faster than print because it does not return a value.
• echo can be used with or without parentheses, which makes it more flexible in certain situations.
• print is useful in expressions where the returned value is required, such as assigning a value to a variable.

In most cases, echo and print can be used interchangeably for outputting strings or variables.

However, echo is more commonly used in PHP code due to its simplicity and flexibility.

What is parser in PHP?

In PHP, a parser refers to a component or module responsible for analyzing and interpreting PHP code. It is an essential part of the PHP interpreter that reads the source code and converts it into a format that can be executed by the PHP runtime.

The PHP parser performs the following tasks:

Tokenization:

• The parser breaks down the PHP source code into individual tokens, which are the smallest units of meaningful code.
• Tokens represent elements such as keywords, variables, operators, strings, and function names.

Syntax Analysis:

• The parser analyzes the structure of the code based on the rules of the PHP language grammar.
• It verifies if the arrangement and combination of tokens conform to the language syntax.
• If any syntax errors are detected, the parser raises appropriate error messages.

Abstract Syntax Tree (AST) Generation:

• The parser builds an Abstract Syntax Tree (AST) from the validated tokens.
• The AST is a hierarchical representation of the code’s structure, where each node represents an element of the code (e.g., function call, loop, conditional statement).
• The AST is used for subsequent stages of code execution and optimization.

Error Handling:

• The parser detects and reports syntax errors, such as missing semicolons, mismatched parentheses, or invalid variable assignments.
• When an error occurs, the parser generates error messages that help developers identify and fix the issues.

Once the parser successfully parses the PHP code and creates the AST, the subsequent stages of the PHP interpreter can execute the code accordingly, including performing variable assignments, function calls, and executing control flow statements.

Overall, the parser plays a crucial role in the PHP execution process by interpreting the code’s structure and ensuring it adheres to the syntax rules of the PHP language.

How can PHP and HTML interact ?

PHP and HTML can interact in several ways to create dynamic web pages and provide data-driven functionality. Here are some common methods of interaction between PHP and HTML:

Embedding PHP code in HTML:

• PHP code can be directly embedded within HTML using PHP tags (<?php … ?> or <? … ?>).
• PHP code within these tags can generate dynamic content, perform calculations, or retrieve data from databases or other sources.
• The output generated by the PHP code is then included in the HTML response sent to the browser.

What is commonly used method in php for Hashing Password?

crypt(), sha1(), sha256() and md5()

What are the features and advantages of PHP?

– Features: Easy integration with HTML, support for various databases, extensive library of functions, object-oriented programming (OOP) support, cross-platform compatibility.

– Advantages: Open-source and free, large community support, easy to learn and deploy, wide range of frameworks and CMS options available.

What are the differences between PHP 5 and PHP 7?

– PHP 7 offers significant performance improvements, reduced memory usage, and improved error handling compared to PHP 5. It introduces new features like scalar type declarations, return type declarations, anonymous classes, and the null coalescing operator.

What are the differences between PHP 7 and PHP 8?

Explain the differences between GET and POST methods in PHP.

– GET: Data is appended to the URL and visible in the browser’s address bar. Suitable for retrieving data and should not be used for sensitive information.

– POST: Data is sent in the HTTP request body and not visible in the address bar. Suitable for sensitive or large data, such as form submissions or file uploads.

How can you prevent SQL injection attacks in PHP?

– Use prepared statements or parameterized queries with placeholders to separate SQL code from data.

– Sanitize user input using functions like `mysqli_real_escape_string()` or use prepared statements with bound parameters.

– Avoid directly inserting user input into SQL queries.

What is the difference between `include` and `require` in PHP?

– Both `include` and `require` are used to include files in PHP.

– `include` generates a warning and continues execution if the file is not found, while `require` generates a fatal error and stops execution.

– `require_once` and `include_once` are similar but ensure the file is included only once, even if multiple inclusion attempts are made.

Explain the difference between `==` and `===` operators in PHP.

– `==` is used for loose comparison and checks if the values of two variables are equal, performing type coercion if necessary.

– `===` is used for strict comparison and checks if the values and types of two variables are equal.

How do you handle file uploads in PHP?

– Use an HTML form with `enctype=”multipart/form-data”` and an `<input type=”file”>` field.

– In PHP, access the uploaded file using the `$_FILES` superglobal, which contains details like file name, size, temporary location, etc.

– Move the file to a permanent location using functions like `move_uploaded_file()`.

These are just a few PHP interview questions and answers. Remember to prepare well and review additional topics depending on the specific job requirements and your level of expertise in PHP.

What are Abstract Classes and Methods?

– An abstract class is a class that contains at least one abstract method. An abstract method is a method that is declared, but not implemented in the code.

* When inheriting from an abstract class, the child class method must be defined with the same name.

when a child class is inherited from an abstract class, we have the following rules:

-The child class method must be defined with the same name and it redeclares the parent abstract method

-The child class method must be defined with the same or a less restricted access modifier

-The number of required arguments must be the same. However, the child class may have optional arguments in addition

What are Interfaces?

– Interfaces allow to specify what methods a class should implement.

– Interfaces make it easy to use a variety of different classes in the same way. When one or more classes use the same interface, it is referred to as “polymorphism”.

Design Pattern:

Design pattern is a way to create an application,by using design pattern we can’t face common software development problems.

some popular design patterns are:

1- Singleton Pattern: Ensures that only one instance of a class is created throughout the application.

This can be useful in scenarios where we need a single point of access to a shared resource or when we want to limit object creation.

2- Factory Pattern: The Factory pattern provides an interface for creating objects without specifying the exact class of the object being created.

It allows for creating objects based on certain conditions or configurations, providing flexibility and decoupling the code from specific class implementations.

3- MVC (Model-View-Controller) Pattern: The MVC pattern separates the application into three major components: the Model (data and business logic), the View (presentation layer), and the Controller (handles user interactions and coordinates the Model and View). It promotes separation of concerns and facilitates modular development.

Differentiate between variables and constants in PHP:

* Variable can be redefined and constant can not be redefined.

* Variable should start with $ and not necessary for constact to start with $.

* Define a variable by simple assignment,Constants can’t be defined by simple assignments. They are defined using the define() function.

Trait:

• A trait in PHP is a code reusability mechanism.
• It allows us to define a set of methods that can be reused in multiple classes.
• Traits provide a way to avoid the limitations of single inheritance, as a class can use multiple traits.
• A trait is declared using the trait keyword.
• A class can use one or more traits by using the use keyword followed by the trait’s name.
• A trait can contain methods, properties, and even abstract methods.
• If a class and a trait both have methods with the same name, the method from the class takes precedence.

trait LoggingTrait {

public function log($message) {

echo “Log: $message\n”;

}

}

class User {

use LoggingTrait;

public function createUser() {

// … logic to create a user …

$this->log(“User created.”);

}

}

class Product {

use LoggingTrait;

public function createProduct() {

// … logic to create a product …

$this->log(“Product created.”);

}

}

$user = new User();

$user->createUser(); // Output: Log: User created.

$product = new Product();

$product->createProduct(); // Output: Log: Product created.