What are common pitfalls when creating a registration/login script in PHP, especially regarding form input handling?

One common pitfall when creating a registration/login script in PHP is not properly sanitizing and validating form input data, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To solve this issue, always sanitize and validate user input before using it in database queries or displaying it on the page. 

// Example of sanitizing and validating form input data in PHP

// Sanitize input data
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$email = filter_var($_POST['email'], FILTER_SANITIZE_EMAIL);
$password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);

// Validate input data
if(empty($username) || empty($email) || empty($password)) {
    // Handle empty fields error
    echo "Please fill in all fields.";
} else {
    // Proceed with registration/login process
}

Keywords

SQL injection XSS attacks password hashing form validation CSRF protection

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