Why is server-side validation necessary even if client-side JavaScript validation is implemented in PHP forms?

Server-side validation is necessary because client-side JavaScript validation can be bypassed by users who disable JavaScript in their browsers or manipulate the code. This means that data can still be submitted to the server without being properly validated, leading to potential security vulnerabilities and data integrity issues. By implementing server-side validation in addition to client-side validation, you can ensure that all data is validated before processing it further. 

// Server-side validation example
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    
    // Validate name field
    if (empty($name)) {
        $errors[] = "Name is required.";
    } else {
        // Additional validation logic
    }
    
    // Check for any validation errors
    if (!empty($errors)) {
        foreach ($errors as $error) {
            echo $error . "<br>";
        }
    } else {
        // Process the form data
    }
}

Keywords

server-side validation client-side JavaScript validation PHP forms security vulnerabilities data integrity

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