How can PHP sessions be used to track user input and prevent multiple submissions of the same answer?

To prevent multiple submissions of the same answer, we can use PHP sessions to track user input. We can store the submitted answer in a session variable and check if the same answer has been submitted before processing the form data. If the answer has already been submitted, we can display an error message to the user. 

session_start();

if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $submittedAnswer = $_POST['answer'];

    if (isset($_SESSION['submitted_answers']) && in_array($submittedAnswer, $_SESSION['submitted_answers'])) {
        echo "Error: You have already submitted this answer.";
    } else {
        // Process the form data
        // Add the submitted answer to the session variable
        $_SESSION['submitted_answers'][] = $submittedAnswer;
    }
}

Keywords

PHP sessions user input prevent multiple submissions form submission session variables

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