Why am I getting random characters prepended to a decrypted value in Node.js?

I am using PHP to encrypt a string using a public key. I then pass the private key to a Node.js microservice for decryption. I am getting a successful decryption, but there is strange encoded characters before the true decrypted value.

PHP Generate Keys & Encrypt Value

$user_passphrase = '***'
$string = '123ABC';

// Generate key pair
$pkey = openssl_pkey_new([
    'private_key_bits' => 2048,
    'private_key_type' => OPENSSL_KEYTYPE_RSA,
]);

// Extract private key
openssl_pkey_export($pkey, $private_key, $user_passphrase);

// Base64 encode private key
$private_key = base64_encode($private_key);

// Extract public key
$pkey_details = openssl_pkey_get_details($pkey);

// Base64 encoded public key
$public_key = base64_encode($pkey_details['key']);

// Encrypt value
openssl_public_encrypt($string, $encrypted_value, base64_decode($public_key));

var_dump('Encrypted Value: ' . base64_encode($encrypted_value));

Node.js Decrypt Value

const crypto = require('crypto');

function decrypt (value, privateKey, passphrase) {
  value = Buffer.from(value, 'base64');
  privateKey = Buffer.from(privateKey, 'base64');

  return crypto.privateDecrypt({
    key: privateKey,
    passphrase: passphrase,
    padding: crypto.constants.RSA_NO_PADDING
  }, value).toString('utf8');
}

const decryptedValue = decrypt(encryptedString, encryptedPrivateKey, userPassphrase);

console.log('Decrypted Value:' + decryptedValue);

When I run the php script, I pass the necessary values to the Node.js script. When the Node.js script decodes the value, the correct decoded value (123ABC) is at the end of a long string with strange encoding characters. Why am I seeing these strange characters?

�R^�z���p��LUZ��ϓ)�V'�5I��T�Z&jzD���TM�d��U�@��3�D�z�ו"��k��I��p���D�?����Oe���Ȯzl�Mss�L��;�j���yX�j�ŭ�]�� 123ABC