What are some common mistakes to avoid when working with POST variables in PHP?

One common mistake when working with POST variables in PHP is not properly sanitizing user input, which can lead to security vulnerabilities such as SQL injection or cross-site scripting attacks. To avoid this, always use functions like `filter_input()` or `mysqli_real_escape_string()` to sanitize user input before using it in your code. 

// Sanitize user input from POST variable
$username = filter_input(INPUT_POST, 'username', FILTER_SANITIZE_STRING);
$password = filter_input(INPUT_POST, 'password', FILTER_SANITIZE_STRING);

// Connect to database and insert sanitized data
$mysqli = new mysqli('localhost', 'username', 'password', 'database');
$stmt = $mysqli->prepare("INSERT INTO users (username, password) VALUES (?, ?)");
$stmt->bind_param('ss', $username, $password);
$stmt->execute();
$stmt->close();
$mysqli->close();

Keywords

POST variables PHP security validation sanitization

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