Section 1.1: What is PHP?

PHP, short for Hypertext Preprocessor, is a server-side scripting language tailored for web development. It is integrated within HTML and executed on the server side. This means PHP processes commands on the server, generating content that is then delivered to the client's browser. Its server-side execution is what distinguishes PHP from client-side scripting languages, making it an effective choice for tasks such as database management and file manipulation.

Section 1.2: Include vs. Require

Both include and require serve the purpose of incorporating external files into a PHP script. However, they differ in their error handling. When using include, if the specified file is absent, a warning is issued, but the script continues to run. On the other hand, a missing file when using require will lead to a fatal error, stopping the script entirely.

Use include for non-essential files where you want the script to proceed even if the file isn't found. Opt for require when the file is critical for the script's operation.

Section 1.3: Echo vs. Print

In PHP, both echo and print are employed to display data, yet they have some subtle distinctions. echo can handle multiple parameters and does not return a value, which makes it slightly faster. Conversely, print accepts a single argument and always returns 1, making it useful when you need to utilize the output in an expression. Generally, echo is favored for its performance and simplicity.

Section 1.4: Understanding Sessions in PHP

Sessions in PHP allow for the retention of user data across various web pages. When a session is initiated, a unique session ID is assigned to the user, which can either be stored as a cookie or appended to the URL. This session ID is crucial for linking user-specific data, such as login credentials or shopping cart items, across different pages. Sessions are essential for maintaining user state and personalizing the browsing experience.

Section 1.5: GET vs. POST in Form Submissions

GET and POST are both HTTP methods used for transmitting data to the server. The GET method appends data to the URL, making it visible in the address bar, while POST sends data in the request body, keeping it concealed. GET is suitable for non-sensitive data and has limitations on the amount of information that can be sent. In contrast, POST is preferable for sensitive information and can accommodate larger datasets.

Section 2.1: mysqli vs. PDO

The "mysqli" (MySQL Improved) and "PDO" (PHP Data Objects) are both libraries used for database access in PHP. "mysqli" is tailored specifically for MySQL databases and offers both procedural and object-oriented interfaces. In contrast, "PDO" serves as a database abstraction layer, supporting various database systems and enabling seamless database switching. Given its versatility, PDO is often regarded as the superior option for developers.

Section 2.2: The Role of htmlspecialchars

The function "htmlspecialchars" is designed to convert special characters in a string into their respective HTML entities. This is essential for preventing security threats, such as cross-site scripting (XSS), by ensuring that user inputs containing HTML or JavaScript are displayed as text rather than executed. It is particularly useful when handling user-generated content to avoid unintended execution of HTML tags or scripts.

Section 2.3: Importance of Namespaces

Namespaces in PHP allow developers to organize and encapsulate code, preventing naming conflicts between various project components or third-party libraries. By implementing namespaces, developers can group related classes, functions, and constants, which not only reduces naming collisions but also enhances modularity and maintainability. This is especially vital in larger projects or when integrating multiple libraries to maintain a clear and organized code structure.

Section 2.4: Autoloading in PHP

Autoloading is a PHP feature that automatically loads classes when they are referenced but not yet defined. This approach minimizes the need for explicit "include" or "require" statements for each class, resulting in cleaner and more maintainable code.

Section 2.5: The Composer Tool

Composer is a dependency manager designed for PHP that streamlines the process of managing libraries and packages within a PHP project. It empowers developers to declare project dependencies and automatically handles their installation and updates. Composer is a vital tool in modern PHP development, enabling seamless integration of third-party libraries, frameworks, and tools.

This video titled "20 Common Interview Questions for PHP Developers" offers an overview of frequently asked questions during PHP interviews. It serves as a valuable resource for developers looking to prepare effectively.