How can server-side validation be implemented to prevent users from bypassing client-side checks for repeated smileys in a shoutbox?

To prevent users from bypassing client-side checks for repeated smileys in a shoutbox, server-side validation can be implemented by checking the input data for any repeated smileys before saving it to the database. This ensures that even if a user tries to manipulate the client-side checks, the server will still catch and prevent the submission of invalid data.

// Check for repeated smileys in the input data before saving to the database
$inputData = $_POST['shout_message'];
if (preg_match('/(:\)|:\(|:D)+/', $inputData)) {
    // Repeated smileys found, display an error message to the user
    echo "Error: Repeated smileys are not allowed in the shoutbox.";
} else {
    // Save the input data to the database
    // Your database saving code here
}