PHP7 OpenSSL DES-EDE-CBC encryption and decryption

<?php
class DesEdeCbc {
private $cipher, $key, $iv;
/**
 * DesEdeCbc constructor.
 * @param $cipher
 * @param $key
 * @param $iv
 */
public function __construct($cipher, $key, $iv) {
$this->cipher = $cipher;
$this->key= $this->getFormatKey($key);
$this->iv = $iv;
}
/**
 * @func  加密
 * @param $msg
 * @return string
 */
public function encrypt($msg) {
$des = @openssl_encrypt($msg, $this->cipher, $this->key, OPENSSL_RAW_DATA, $this->iv);
return base64_encode($des);
}
/**
 * @func  解密
 * @param $msg
 * @return string
 */
public function decrypt($msg) {
return @openssl_decrypt(base64_decode($msg), $this->cipher, $this->key, OPENSSL_RAW_DATA, $this->iv);
}
/**
 * @func  生成24位长度的key
 * @param $skey
 * @return bool|string
 */
private function getFormatKey($skey) {
$md5Value= md5($skey);
$md5ValueLen = strlen($md5Value);
$key = $md5Value . substr($md5Value, 0, $md5ValueLen / 2);
return hex2bin($key);
}
}
$cipher = &#39;DES-EDE-CBC&#39;;
$msg = &#39;HelloWorld&#39;;
$key = &#39;12345678&#39;;
$iv  = "\x00\x00\x00\x00\x00\x00\x00\x00";
$des = new DesEdeCbc($cipher, $key, $iv);
// 加密
$msg = $des->encrypt($msg);
echo &#39;加密后: &#39; . $msg . PHP_EOL;
// 解密
$src = $des->decrypt($msg);
echo &#39;解密后: &#39; . $src . PHP_EOL;