In the realm of web development, user input is a double-edged sword. While it provides the lifeblood for interactive applications, it also harbors potential security threats if not handled with care. Malicious users can exploit vulnerabilities in your code to inject harmful code, leading to serious security breaches. Sanitizing user input is the process of filtering and cleansing data received from users to remove any potentially harmful elements. It's like erecting a barrier between your application and the outside world, preventing untrusted data from infiltrating your codebase. PHP offers a variety of built-in functions to effectively sanitize user input, making it easier to safeguard your applications from common security vulnerabilities. Let's delve into some of these key functions and explore their usage: 1. htmlspecialchars(): This function protects against cross-site scripting (XSS) attacks by converting certain characters, such as '<', '>