Why is it recommended to validate user input server-side rather than relying solely on client-side validation?

It is recommended to validate user input server-side because client-side validation can be easily bypassed by malicious users. Server-side validation ensures that data is validated on the server before processing it, providing an additional layer of security. This approach helps prevent vulnerabilities such as SQL injection and cross-site scripting attacks. 

// Server-side validation example
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = $_POST["username"];
    $password = $_POST["password"];
    
    // Validate input
    if (empty($username) || empty($password)) {
        echo "Username and password are required.";
    } else {
        // Process the data
        // Additional validation and processing logic here
    }
}

Keywords

PHP server-side validation user input security data validation

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