What are some best practices for checking if a user has participated in multiple surveys before allowing them to enter a contest in PHP?

To prevent users from entering a contest multiple times by participating in multiple surveys, we can store the user's unique identifier (such as their email or user ID) in a database table each time they participate in a survey. Before allowing them to enter the contest, we can check if their identifier already exists in the table to determine if they have participated in multiple surveys. 

// Connect to the database
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

$conn = new mysqli($servername, $username, $password, $dbname);

// Check if user has participated in multiple surveys
$user_id = $_SESSION['user_id']; // Assuming user ID is stored in a session variable
$sql = "SELECT COUNT(*) as count FROM survey_participants WHERE user_id = $user_id";
$result = $conn->query($sql);
$row = $result->fetch_assoc();

if ($row['count'] > 1) {
    echo "Sorry, you have already participated in multiple surveys and are not eligible to enter the contest.";
} else {
    echo "Congratulations! You are eligible to enter the contest.";
}

Keywords

PHP user participation surveys contest entry validation

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