PHP でデータの暗号化および復号化関数を実装する方法

<?php
$data = "Hello, World!";
$encryptedData = md5($data);
echo "加密后的数据: " . $encryptedData;
?>

<?php
function encrypt($data, $key) {
    $iv = mcrypt_create_iv(
        mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC),
        MCRYPT_DEV_URANDOM
    );
    $encrypted = base64_encode(
        $iv . mcrypt_encrypt(
            MCRYPT_RIJNDAEL_128,
            hash('sha256', $key, true),
            $data,
            MCRYPT_MODE_CBC,
            $iv
        )
    );
    return $encrypted;
}

function decrypt($data, $key) {
    $data = base64_decode($data);
    $iv = substr($data, 0, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC));
    $decrypted = rtrim(
        mcrypt_decrypt(
            MCRYPT_RIJNDAEL_128,
            hash('sha256', $key, true),
            substr($data, mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_CBC)),
            MCRYPT_MODE_CBC,
            $iv
        ),
        ""
    );
    return $decrypted;
}

$data = "Hello, World!";
$key = "testkey";
$encryptedData = encrypt($data, $key);
$decryptedData = decrypt($encryptedData, $key);

echo "原始数据: " . $data;
echo "加密后的数据: " . $encryptedData;
echo "解密后的数据: " . $decryptedData;
?>