What are the basic principles of web development that beginners should be aware of when using PHP?

Beginners in web development using PHP should be aware of the basic principles such as understanding the syntax and structure of PHP, learning how to properly handle form data, utilizing functions and loops effectively, and implementing security measures to prevent common vulnerabilities like SQL injection and cross-site scripting.

// Example of handling form data in PHP
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = $_POST["username"];
    $password = $_POST["password"];
    
    // Perform necessary validation and processing of form data
}