PHP AES は AES/ECB/PKCS7Padding パディング モード暗号化を使用し、PHP 7 バージョンと互換性があります。

リファレンスマニュアルhttp://www.php.net/manual/en/function.openssl-decrypt.php

class Security{
        public static function encrypt($input, $key) {
            if (substr(PHP_VERSION, 0, 1) == '7') {
                return self::opensslEncrypt($input,$key);
            }else{
                return self::mcryptEncrypt($input,$key);
            }

        }
        public static function decrypt($input, $key) {
            if (substr(PHP_VERSION, 0, 1) == '7') {
                return self::opensslDecrypt($input,$key);
            }else{
                return self::mcryptDecrypt($input,$key);
            }
    
        }
        /**
         * [encrypt description]
         * 使用mcrypt库进行加密
         * @param  [type] $input
         * @param  [type] $key
         * @return [type]
         */
        public static function mcryptEncrypt($input, $key) {
            $size = mcrypt_get_block_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB);
            $input = self::pkcs5Pad($input, $size);
            $td = mcrypt_module_open(MCRYPT_RIJNDAEL_128, '', MCRYPT_MODE_ECB, '');
            $iv = mcrypt_create_iv (mcrypt_enc_get_iv_size($td), MCRYPT_RAND);//MCRYPT_DEV_URANDOM
            mcrypt_generic_init($td, $key, $iv);
            $data = mcrypt_generic($td, $input);
            mcrypt_generic_deinit($td);
            mcrypt_module_close($td);
            $data = base64_encode($data);
            return $data;
        }
        /**
         * [pkcs5Pad description]
         * @param  [type] $text
         * @param  [type] $blocksize
         * @return [type]
         */
        private static function pkcs5Pad($text, $blocksize) {
            $pad = $blocksize - (strlen($text) % $blocksize);
            return $text . str_repeat(chr($pad), $pad);
        }
        /**
         * [decrypt description]
         * 使用mcrypt库进行解密
         * @param  [type] $sStr
         * @param  [type] $sKey
         * @return [type]
         */
        public static function mcryptDecrypt($sStr, $sKey) {
            $iv = mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_128, MCRYPT_MODE_ECB), MCRYPT_RAND);//MCRYPT_DEV_URANDOM
            $decrypted = mcrypt_decrypt(MCRYPT_RIJNDAEL_128, $sKey, base64_decode($sStr), MCRYPT_MODE_ECB, $iv);
            $dec_s = strlen($decrypted);
            $padding = ord($decrypted[$dec_s-1]);
            $decrypted = substr($decrypted, 0, -$padding);
            return $decrypted;
        }
        /**
         * [opensslDecrypt description]
         * 使用openssl库进行加密
         * @param  [type] $sStr
         * @param  [type] $sKey
         * @return [type]
         */
        public static function opensslEncrypt($sStr, $sKey, $method = 'AES-256-ECB'){
            $str = openssl_encrypt($sStr,$method,$sKey);
            return $str;
        }
        /**
         * [opensslDecrypt description]
         * 使用openssl库进行解密
         * @param  [type] $sStr
         * @param  [type] $sKey
         * @return [type]
         */
        public static function opensslDecrypt($sStr, $sKey, $method = 'AES-256-ECB'){
            $str = openssl_decrypt($sStr,$method,$sKey);
            return $str;
        }
}