What is the difference between server-side and client-side control in PHP?

Server-side control in PHP refers to processing and handling data on the server before sending it to the client, ensuring that sensitive information and critical operations are managed securely. On the other hand, client-side control involves manipulating data on the user's browser using JavaScript, which can enhance user experience but may expose vulnerabilities if not handled properly. To implement server-side control in PHP, you can validate user input, sanitize data, and perform necessary operations before sending a response to the client.

// Server-side control example
$userInput = $_POST['user_input'];

// Validate user input
if(!empty($userInput)){
    // Sanitize data
    $sanitizedInput = filter_var($userInput, FILTER_SANITIZE_STRING);

    // Perform necessary operations
    $result = doSomething($sanitizedInput);

    // Send response to client
    echo $result;
} else {
    echo "Invalid input";
}

function doSomething($data){
    // Perform some operation
    return "Processed: " . $data;
}