JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech III WEB TECHNOLOGIES Previous Question Paper (January/February - 2021 - R16)

To create a secure PHP form for user authentication, we define an HTML form that submits data to a PHP script using the POST method. The PHP script then performs server-side validation to ensure the fields are not empty and meet security requirements.

The following HTML structure creates the input fields:

<form method="post" action="login.php">
  User ID: <input type="text" name="userid" required><br>
  Password: <input type="password" name="password" required><br>
  <input type="submit" value="Login">
</form>

The server-side PHP validation script processes the input:

<?php
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    $userid = trim($_POST['userid']);
    $password = $_POST['password'];

    if (empty($userid) || empty($password)) {
        echo "User ID and Password are required.";
    } elseif (strlen($password) < 8) {
        echo "Password must be at least 8 characters long.";
    } else {
        // Sanitize input to prevent XSS
        $userid = htmlspecialchars($userid);
        echo "Validation successful for user: " . $userid;
    }
}
?>

Key validation steps include:

• Empty Check: Using empty() to ensure fields are not submitted blank.
• Sanitization: Applying htmlspecialchars() to prevent Cross-Site Scripting (XSS) attacks.
• Input Trimming: Using trim() to remove unnecessary whitespace from the User ID.
• Length Validation: Ensuring the password meets minimum complexity requirements before processing.