What are common pitfalls when sending data from client-side scripts to a PHP server?

One common pitfall when sending data from client-side scripts to a PHP server is not properly sanitizing and validating the input data. This can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To solve this issue, always sanitize and validate any data received from client-side scripts before processing it in your PHP server code.

// Example of sanitizing and validating input data in PHP
$user_input = $_POST['user_input'];

// Sanitize input data
$sanitized_input = filter_var($user_input, FILTER_SANITIZE_STRING);

// Validate input data
if (strlen($sanitized_input) > 0) {
    // Process the sanitized input data
    echo "Input data is valid: " . $sanitized_input;
} else {
    echo "Invalid input data";
}