使用OpenSSL加密/解密的PHP对我不起作用

我正在尝试使用PHP和OpenSSL使用公钥加密一些数据，然后再次解密。

我使用以下代码生成了公共.key和私有.key：

// generate private key
$privateKey = openssl_pkey_new(array(
    'private_key_bits' => 1024,
    'private_key_type' => OPENSSL_KEYTYPE_RSA,
));
// write private key to file
openssl_pkey_export_to_file($privateKey, 'private.key');
// generate public key from private key
$publicKey = openssl_pkey_get_details($privateKey);
// write public key to file
file_put_contents('public.key', $publicKey['key']);
// clear key
openssl_free_key($privateKey);

我的加密和解密代码基本上直接来自PHP文档：

// data to encrypt
$data = "This is a long string or other bit of data that i want to encrypt";
// ==== ENCRYPT ====
// read public key
$publicKey =  file_get_contents("public.key");
$publicKey = openssl_get_publickey($publicKey);
// encrypt data using public key into $sealed
$sealed = '';
openssl_seal($data, $sealed, $ekeys, array($publicKey));
openssl_free_key($publicKey);
// ==== DECRYPT ====
// get private key to decrypt with
$privateKey = file_get_contents("private.key");
$privateKey = openssl_get_privatekey($privateKey);
// decrypt data using private key into $open
$open = '';
openssl_open($sealed, $open, $env_key, $privateKey);
openssl_free_key($privateKey);

// display decrypted data:
echo "<p>Decrypted data: ".$open;

任何人都知道为什么它不起作用，或者至少是一种找出正在发生的错误的方法？