What are the potential pitfalls of comparing form input with database values in PHP?

When comparing form input with database values in PHP, potential pitfalls include SQL injection attacks if the input is not properly sanitized, and the risk of exposing sensitive information if the comparison is not done securely. To mitigate these risks, it is important to use prepared statements and parameterized queries when interacting with the database to prevent SQL injection attacks. Additionally, sensitive information should not be directly compared in plain text, but rather hashed and securely compared. 

// Using prepared statements and parameterized queries to compare form input with database values securely
$stmt = $pdo->prepare("SELECT * FROM users WHERE username = :username");
$stmt->bindParam(':username', $username);
$stmt->execute();

$user = $stmt->fetch();

if ($user && password_verify($password, $user['password'])) {
    // User authenticated successfully
} else {
    // Authentication failed
}

Keywords

SQL injection data validation prepared statements PDO XSS.

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