How can PHP developers ensure secure variable handling in their code?

PHP developers can ensure secure variable handling by properly sanitizing and validating user input, using prepared statements for database queries to prevent SQL injection, and avoiding the use of global variables to prevent variable contamination. Additionally, developers should use secure coding practices such as input validation, output escaping, and data encryption to protect sensitive information. 

// Example of sanitizing user input
$username = filter_var($_POST['username'], FILTER_SANITIZE_STRING);

// Example of using prepared statements for database queries
$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username');
$stmt->bindParam(':username', $username);
$stmt->execute();

// Example of avoiding global variables
function getUserData($userId) {
    global $pdo; // Avoid using global variables
    $stmt = $pdo->prepare('SELECT * FROM users WHERE id = :id');
    $stmt->bindParam(':id', $userId);
    $stmt->execute();
    return $stmt->fetch();
}

Keywords

SQL injection cross-site scripting input validation prepared statements secure coding practices

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