Why is client-side validation not enough to prevent incorrect data input in PHP forms?

Client-side validation is not enough to prevent incorrect data input in PHP forms because it can be easily bypassed by users who disable JavaScript or manipulate the form data before submission. To ensure data integrity, server-side validation in PHP should also be implemented to validate and sanitize user input before processing it. 

// Server-side validation in PHP
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $name = $_POST["name"];
    
    // Validate input
    if (empty($name)) {
        $errors[] = "Name is required";
    }
    
    // Sanitize input
    $name = filter_var($name, FILTER_SANITIZE_STRING);
    
    // Process the form data
    if (empty($errors)) {
        // Process the form data
    } else {
        foreach ($errors as $error) {
            echo $error . "<br>";
        }
    }
}

Keywords

client-side validation PHP forms incorrect data input server-side validation data validation

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