What are the best practices for validating and sanitizing user input in PHP forms?

Validating and sanitizing user input in PHP forms is crucial to prevent security vulnerabilities such as SQL injection, cross-site scripting (XSS), and other malicious attacks. To validate user input, you can use PHP functions like filter_var() or regular expressions to ensure the data meets the expected format. Sanitizing user input involves removing any potentially harmful characters or tags using functions like htmlspecialchars() or htmlentities(). 

// Example of validating and sanitizing user input in PHP form
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = filter_var($_POST["username"], FILTER_SANITIZE_STRING);
    $email = filter_var($_POST["email"], FILTER_SANITIZE_EMAIL);

    // Validate email format
    if (!filter_var($email, FILTER_VALIDATE_EMAIL)) {
        echo "Invalid email format";
    }

    // Sanitize input to prevent XSS attacks
    $comment = htmlspecialchars($_POST["comment"]);

    // Process the sanitized data
    // (e.g., insert into database, send email, etc.)
}

Keywords

filter_var htmlspecialchars validation sanitization XSS

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