How important is it to implement server-side validation in addition to client-side validation for user inputs in PHP applications?

It is crucial to implement server-side validation in addition to client-side validation for user inputs in PHP applications. Client-side validation can easily be bypassed by users who have some technical knowledge, so server-side validation ensures that all inputs are properly validated before processing them. This helps prevent security vulnerabilities and ensures data integrity. 

// Server-side validation example
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $username = $_POST['username'];
    $password = $_POST['password'];

    // Validate inputs
    if (empty($username) || empty($password)) {
        echo "Please fill in all fields";
    } else {
        // Process the input data
    }
}

Keywords

PHP server-side validation client-side validation user inputs security.

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