What are some common mistakes to avoid when validating form input in PHP?

One common mistake to avoid when validating form input in PHP is not properly sanitizing user input, which can leave your application vulnerable to SQL injection attacks. To solve this issue, always sanitize input data using functions like `htmlspecialchars()` or prepared statements before using it in database queries. 

// Sanitize user input using htmlspecialchars()
$username = htmlspecialchars($_POST['username']);
$email = htmlspecialchars($_POST['email']);

// Use prepared statements to prevent SQL injection
$stmt = $pdo->prepare("INSERT INTO users (username, email) VALUES (:username, :email)");
$stmt->bindParam(':username', $username);
$stmt->bindParam(':email', $email);
$stmt->execute();

Keywords

form input validation PHP htmlspecialchars filter_var error handling

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