What are some common pitfalls to avoid when handling user input in PHP forms that interact with a database?

One common pitfall to avoid when handling user input in PHP forms that interact with a database is SQL injection. To prevent this, always sanitize and validate user input before using it in database queries. Use prepared statements or parameterized queries to safely interact with the database. 

// Example of using prepared statements to handle user input safely

// Assuming $db is your database connection

// Sanitize and validate user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);
$password = filter_var($_POST['password'], FILTER_SANITIZE_STRING);

// Prepare a SQL statement with placeholders
$stmt = $db->prepare("SELECT * FROM users WHERE username = ? AND password = ?");
$stmt->bind_param("ss", $username, $password);

// Execute the statement
$stmt->execute();

// Handle the results
$result = $stmt->get_result();
if ($result->num_rows > 0) {
    // User authenticated
} else {
    // Invalid credentials
}

// Close the statement and database connection
$stmt->close();
$db->close();

Keywords

SQL injection form validation prepared statements cross-site scripting input sanitization

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