AES GCM是一种高级加密标准的加密算法，可在不失去安全性的前提下实现高效的加密操作。下面分别介绍使用C#和PHP实现AES GCM加密的方法，并对两者进行比较。

C#实现AES GCM加密：

using System.Security.Cryptography;
using System.Text;

public static byte[] AESEncrypt(string plainText, byte[] key, byte[] iv)
{
    byte[] encrypted;
    using (Aes aesAlg = Aes.Create())
    {
        aesAlg.Key = key;
        aesAlg.IV = iv;
        aesAlg.Mode = CipherMode.GCM;
        aesAlg.Padding = PaddingMode.None;

        ICryptoTransform encryptor = aesAlg.CreateEncryptor(aesAlg.Key, aesAlg.IV);

        using (MemoryStream msEncrypt = new MemoryStream())
        {
            using (CryptoStream csEncrypt = new CryptoStream(msEncrypt, encryptor, CryptoStreamMode.Write))
            {
                using (StreamWriter swEncrypt = new StreamWriter(csEncrypt))
                {
                    swEncrypt.Write(plainText);
                }
                encrypted = msEncrypt.ToArray();
            }
        }
    }
    return encrypted;
}

PHP实现AES GCM加密：

function AESEncrypt($key, $iv, $data)
{
    $cipher = "aes-256-gcm";
    $options = OPENSSL_RAW_DATA;
    $tag_length = 16;

    // Generate a random initialization vector (IV)
    if (empty($iv)) {
        $iv_length = openssl_cipher_iv_length($cipher);
        $iv = openssl_random_pseudo_bytes($iv_length);
    }

    $encrypted = openssl_encrypt($data, $cipher, $key, $options, $iv, $tag, "", $tag_length);

    // Return IV and encrypted data
    return [
        "iv" => base64_encode($iv),
        "data" => base64_encode($encrypted),
        "tag" => base64_encode($tag),
    ];
}

比较：C#实现的代码使用了.NET自带的加密库，而PHP实现的代码