How can the use of $_REQUEST and $_POST variables impact the security of PHP applications?

Using $_REQUEST and $_POST variables directly in PHP applications can lead to security vulnerabilities such as SQL injection and cross-site scripting attacks. To mitigate these risks, it is recommended to sanitize and validate user input before using it in the application. 

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

// Use prepared statements to prevent SQL injection
$stmt = $pdo->prepare('SELECT * FROM users WHERE username = :username AND password = :password');
$stmt->execute(['username' => $username, 'password' => $password]);

// Rest of the code to handle user authentication

Keywords

$_REQUEST $_POST security PHP applications variables

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