如何在php中加密和解密字符串？

<?php
function encrypt($string, $key) {
    $cipher = "AES-256-CBC";
    $ivlen = openssl_cipher_iv_length($cipher);
    $iv = openssl_random_pseudo_bytes($ivlen);
    $ciphertext = openssl_encrypt($string, $cipher, $key, OPENSSL_RAW_DATA, $iv);
    $hmac = hash_hmac('sha256', $ciphertext, $key, true);
    return base64_encode($iv . $hmac . $ciphertext);
}

function decrypt($string, $key) {
    $c = base64_decode($string);
    $cipher = "AES-256-CBC";
    $ivlen = openssl_cipher_iv_length($cipher);
    $iv = substr($c, 0, $ivlen);
    $hmac = substr($c, $ivlen, $sha2len = 32);
    $ciphertext = substr($c, $ivlen + $sha2len);
    $original_plaintext = openssl_decrypt($ciphertext, $cipher, $key, OPENSSL_RAW_DATA, $iv);
    $calcmac = hash_hmac('sha256', $ciphertext, $key, true);
    if (hash_equals($hmac, $calcmac)) {
        return $original_plaintext;
    }
    return false;
}

// 示例用法
$key = "ThisIsASecretKey";
$string = "Hello World";

$encrypted = encrypt($string, $key);
echo "加密后的字符串：" . $encrypted . "\n";

$decrypted = decrypt($encrypted, $key);
echo "解密后的字符串：" . $decrypted . "\n";
?>