A class for encrypting and decrypting data

<?php 
require_once('/xampp/php/lib/defuse-crypto.phar'); 
use Defuse\Crypto\Key; 
use Defuse\Crypto\Crypto; 
use Defuse\Crypto\Exception\WrongKeyOrModifiedCiphertextException;

class Crypt {
  private $key; public function __construct() { 
    // make sure the following code points to a file that exists
    // and contains a valid key 
    $keyAscii = file_get_contents('/xampp/php/defuse-key.txt'); 
    $this->key = Key::loadFromAsciiSafeString($keyAscii); 
  }
  public function encrypt($data) {
    $encrypted_data = Crypto::encrypt($data, $this->key); 
    return $encrypted_data;
  }
  public function decrypt($encrypted_data) {
    try {
      $data = Crypto::decrypt($encrypted_data, $this->key);
      return $data;
    } catch (WrongKeyOrModifiedCiphertextException $ex) {
      throw new Exception($ex->getMessage());
    }
  }
} ?>

<?php
require 'crypt.php';
$credit_card_no = '4111111111111111'; 

// Create the Crypt object 
$crypt = new Crypt(); 

// Use the Crypt object to encrypt the data 
$encrypted_data = $crypt->encrypt($credit_card_no); 
echo("Encrypted data: $encrypted_data<br />>");

// Use the Crypt object to decrypt the data 
try {
  $decrypted_data = $crypt->decrypt($encrypted_data);
  echo"Decrypted data: $decrypted_data<br />>");
} catch (Exception $ex) {
  echo("Exception: " . $ex->getMessage() . "<br />");
}