How can PHP developers handle user authentication and prevent fraud in online surveys for users with dynamic IP addresses or shared networks?

Handling user authentication and preventing fraud in online surveys for users with dynamic IP addresses or shared networks can be done by implementing a combination of techniques such as session management, user agent tracking, and CAPTCHA verification. By using these methods, developers can verify the identity of users and reduce the risk of fraudulent responses. 

// PHP code snippet for handling user authentication and preventing fraud in online surveys

// Start session
session_start();

// Check user agent to track unique users
$user_agent = $_SERVER['HTTP_USER_AGENT'];

// Check if CAPTCHA verification is successful
if($_POST['captcha'] == $_SESSION['captcha_code']){
    // Authentication successful, proceed with survey
} else {
    // CAPTCHA verification failed, show error message
    echo "CAPTCHA verification failed. Please try again.";
}

Keywords

PHP user authentication fraud prevention dynamic IP addresses shared networks

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