请问PHP如何通过openssl实现AES-256加密算法？

我知道PHP有提供openssl模块，但是我对这个模块不了解，请问有没有了解的朋友。非常感谢。

---

function encrypt($value, $key = '1234567891234567')
{
    $length = mb_strlen($key, '8bit');

    if (!$length === 16) {
        return false;
    }

    $seeds  = '0123456789abcdefghijklmnopqrstuvwxyz';
    $length = 16;

    $iv = substr(str_shuffle(str_repeat($seeds, $length)), 0, $length);

    $value = \openssl_encrypt(serialize($value), 'AES-128-CBC', $key, 0, $iv);

    if ($value === false) {
        return false;
    }

    $iv = base64_encode($iv);

    $mac = hash_hmac('sha256', $iv.$value, $key);

    $json = json_encode(compact('iv', 'value', 'mac'));

    if (! is_string($json)) {
        return false;
    }

    return base64_encode($json);
}

function decrypt($payload, $key = '1234567891234567')
{
    $length = mb_strlen($key, '8bit');

    if (!$length === 16) {
        return false;
    }

    $payload = json_decode(base64_decode($payload), true);

    if (! $payload || ! is_array($payload) || ! isset($payload['iv']) || ! isset($payload['value']) || ! isset($payload['mac'])) {
        return false;
    }

    $seeds  = '0123456789abcdefghijklmnopqrstuvwxyz';
    $length = 16;

    $bytes   = substr(str_shuffle(str_repeat($seeds, $length)), 0, $length);
    $hash    = hash_hmac('sha256', $payload['iv'].$payload['value'], $key);
    $calcMac = hash_hmac('sha256', $hash, $bytes, true);

    if (! hash_equals(hash_hmac('sha256', $payload['mac'], $bytes, true), $calcMac)) {
        return false;
    }

    $iv = base64_decode($payload['iv']);

    $decrypted = \openssl_decrypt($payload['value'], 'AES-128-CBC', $key, 0, $iv);

    if ($decrypted === false) {
        return false;
    }

    return unserialize($decrypted);
}

$str = '123456';
$encrypt = encrypt($str);
$decrypt = decrypt($encrypt);
var_dump($decrypt);

随便写的，看着用吧