What security considerations should be taken into account when implementing an online backup script in PHP?

When implementing an online backup script in PHP, it is crucial to consider security measures to protect sensitive data. One important consideration is to ensure that the backup files are stored in a secure location with restricted access. Additionally, it is essential to encrypt the backup files to prevent unauthorized access. Finally, implementing proper authentication and authorization mechanisms can help prevent malicious attacks on the backup script.

// Example code snippet for encrypting backup files before storing them
$backupData = "sensitive data to be backed up";
$encryptionKey = "yourEncryptionKey";

// Encrypt the backup data
$encryptedData = openssl_encrypt($backupData, 'AES-256-CBC', $encryptionKey, 0, 'yourInitializationVector');

// Store the encrypted data in a secure location
file_put_contents('backup.enc', $encryptedData);