How can PHP developers ensure data security and prevent unauthorized access to files or databases?

To ensure data security and prevent unauthorized access to files or databases in PHP, developers can use secure coding practices such as input validation, using parameterized queries for database interactions, implementing proper authentication and authorization mechanisms, and securing sensitive data with encryption. 

// Example of input validation to prevent SQL injection
$username = mysqli_real_escape_string($conn, $_POST['username']);
$password = mysqli_real_escape_string($conn, $_POST['password']);

// Example of using parameterized queries to prevent SQL injection
$stmt = $conn->prepare("SELECT * FROM users WHERE username = ?");
$stmt->bind_param("s", $username);
$stmt->execute();
$result = $stmt->get_result();

// Example of implementing authentication and authorization
if ($result->num_rows > 0) {
    $user = $result->fetch_assoc();
    if (password_verify($password, $user['password'])) {
        // User authenticated, proceed with authorized actions
    } else {
        // Invalid password
    }
} else {
    // User not found
}

// Example of encrypting sensitive data
$encryptedData = openssl_encrypt($data, 'AES-256-CBC', $encryptionKey, 0, $iv);

Keywords

Data encryption SQL injection Cross-site scripting Access control Secure file permissions

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