如何在php中使用私钥生成签名

$config = array(
    "digest_alg" => "sha256",
    "private_key_bits" => 2048,
    "private_key_type" => OPENSSL_KEYTYPE_RSA,
);

// 生成私钥和公钥
$res = openssl_pkey_new($config);
openssl_pkey_export($res, $privateKey);
$publicKey = openssl_pkey_get_details($res)['key'];

$data = "待签名的数据";
$signature = '';
openssl_sign($data, $signature, $privateKey, OPENSSL_ALGO_SHA256);

$isValid = openssl_verify($data, $signature, $publicKey, OPENSSL_ALGO_SHA256);
if ($isValid === 1) {
    echo "签名验证通过";
} elseif ($isValid === 0) {
    echo "签名验证失败";
} else {
    echo "验证过程发生错误";
}