Encrypt and decrypt between programming languages (PHP & JavaScript).

Encryption.js

/**
 * Encryption class for encrypt/decrypt that works between programming languages.
 * 
 * @author Vee Winch.
 * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
 * @link https://github.com/brix/crypto-js/releases crypto-js.js can be download from here.
 */
class Encryption {


    /**
     * @var integer Return encrypt method or Cipher method number. (128, 192, 256)
     */
    get encryptMethodLength() {
        var encryptMethod = this.encryptMethod;
        // get only number from string.
        // @link https://stackoverflow.com/a/10003709/128761 Reference.
        var aesNumber = encryptMethod.match(/\d+/)[0];
        return parseInt(aesNumber);
    }// encryptMethodLength


    /**
     * @var integer Return cipher method divide by 8. example: AES number 256 will be 256/8 = 32.
     */
    get encryptKeySize() {
        var aesNumber = this.encryptMethodLength;
        return parseInt(aesNumber / 8);
    }// encryptKeySize


    /**
     * @link http://php.net/manual/en/function.openssl-get-cipher-methods.php Refer to available methods in PHP if we are working between JS & PHP encryption.
     * @var string Cipher method. 
     *              Recommended AES-128-CBC, AES-192-CBC, AES-256-CBC 
     *              due to there is no `openssl_cipher_iv_length()` function in JavaScript 
     *              and all of these methods are known as 16 in iv_length.
     */
    get encryptMethod() {
        return 'AES-256-CBC';
    }// encryptMethod


    /**
     * Decrypt string.
     * 
     * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
     * @link https://stackoverflow.com/questions/25492179/decode-a-base64-string-using-cryptojs Crypto JS base64 encode/decode reference.
     * @param string encryptedString The encrypted string to be decrypt.
     * @param string key The key.
     * @return string Return decrypted string.
     */
    decrypt(encryptedString, key) {
        var json = JSON.parse(CryptoJS.enc.Utf8.stringify(CryptoJS.enc.Base64.parse(encryptedString)));

        var salt = CryptoJS.enc.Hex.parse(json.salt);
        var iv = CryptoJS.enc.Hex.parse(json.iv);

        var encrypted = json.ciphertext;// no need to base64 decode.

        var iterations = parseInt(json.iterations);
        if (iterations <= 0) {
            iterations = 999;
        }
        var encryptMethodLength = (this.encryptMethodLength/4);// example: AES number is 256 / 4 = 64
        var hashKey = CryptoJS.PBKDF2(key, salt, {'hasher': CryptoJS.algo.SHA512, 'keySize': (encryptMethodLength/8), 'iterations': iterations});

        var decrypted = CryptoJS.AES.decrypt(encrypted, hashKey, {'mode': CryptoJS.mode.CBC, 'iv': iv});

        return decrypted.toString(CryptoJS.enc.Utf8);
    }// decrypt


    /**
     * Encrypt string.
     * 
     * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
     * @link https://stackoverflow.com/questions/25492179/decode-a-base64-string-using-cryptojs Crypto JS base64 encode/decode reference.
     * @param string string The original string to be encrypt.
     * @param string key The key.
     * @return string Return encrypted string.
     */
    encrypt(string, key) {
        var iv = CryptoJS.lib.WordArray.random(16);// the reason to be 16, please read on `encryptMethod` property.

        var salt = CryptoJS.lib.WordArray.random(256);
        var iterations = 999;
        var encryptMethodLength = (this.encryptMethodLength/4);// example: AES number is 256 / 4 = 64
        var hashKey = CryptoJS.PBKDF2(key, salt, {'hasher': CryptoJS.algo.SHA512, 'keySize': (encryptMethodLength/8), 'iterations': iterations});

        var encrypted = CryptoJS.AES.encrypt(string, hashKey, {'mode': CryptoJS.mode.CBC, 'iv': iv});
        var encryptedString = CryptoJS.enc.Base64.stringify(encrypted.ciphertext);

        var output = {
            'ciphertext': encryptedString,
            'iv': CryptoJS.enc.Hex.stringify(iv),
            'salt': CryptoJS.enc.Hex.stringify(salt),
            'iterations': iterations
        };

        return CryptoJS.enc.Base64.stringify(CryptoJS.enc.Utf8.parse(JSON.stringify(output)));
    }// encrypt


}

Encryption.php

<?php


/**
 * Encryption class for encrypt/decrypt that works between programming languages.
 *
 * @author Vee Winch.
 * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
 */
class Encryption
{


    /**
     * @link http://php.net/manual/en/function.openssl-get-cipher-methods.php Available methods.
     * @var string Cipher method. Recommended AES-128-CBC, AES-192-CBC, AES-256-CBC
     */
    protected $encryptMethod = 'AES-256-CBC';


    /**
     * Decrypt string.
     * 
     * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
     * @param string $encryptedString The encrypted string that is base64 encode.
     * @param string $key The key.
     * @return mixed Return original string value. Return null for failure get salt, iv.
     */
    public function decrypt($encryptedString, $key)
    {
        $json = json_decode(base64_decode($encryptedString), true);

        try {
            $salt = hex2bin($json["salt"]);
            $iv = hex2bin($json["iv"]);
        } catch (Exception $e) {
            return null;
        }

        $cipherText = base64_decode($json['ciphertext']);

        $iterations = intval(abs($json['iterations']));
        if ($iterations <= 0) {
            $iterations = 999;
        }
        $hashKey = hash_pbkdf2('sha512', $key, $salt, $iterations, ($this->encryptMethodLength() / 4));
        unset($iterations, $json, $salt);

        $decrypted= openssl_decrypt($cipherText , $this->encryptMethod, hex2bin($hashKey), OPENSSL_RAW_DATA, $iv);
        unset($cipherText, $hashKey, $iv);

        return $decrypted;
    }// decrypt


    /**
     * Encrypt string.
     * 
     * @link https://stackoverflow.com/questions/41222162/encrypt-in-php-openssl-and-decrypt-in-javascript-cryptojs Reference.
     * @param string $string The original string to be encrypt.
     * @param string $key The key.
     * @return string Return encrypted string.
     */
    public function encrypt($string, $key)
    {
        $ivLength = openssl_cipher_iv_length($this->encryptMethod);
        $iv = openssl_random_pseudo_bytes($ivLength);
 
        $salt = openssl_random_pseudo_bytes(256);
        $iterations = 999;
        $hashKey = hash_pbkdf2('sha512', $key, $salt, $iterations, ($this->encryptMethodLength() / 4));

        $encryptedString = openssl_encrypt($string, $this->encryptMethod, hex2bin($hashKey), OPENSSL_RAW_DATA, $iv);

        $encryptedString = base64_encode($encryptedString);
        unset($hashKey);

        $output = ['ciphertext' => $encryptedString, 'iv' => bin2hex($iv), 'salt' => bin2hex($salt), 'iterations' => $iterations];
        unset($encryptedString, $iterations, $iv, $ivLength, $salt);

        return base64_encode(json_encode($output));
    }// encrypt


    /**
     * Get encrypt method length number (128, 192, 256).
     * 
     * @return integer.
     */
    protected function encryptMethodLength()
    {
        $number = filter_var($this->encryptMethod, FILTER_SANITIZE_NUMBER_INT);

        return intval(abs($number));
    }// encryptMethodLength


    /**
     * Set encryption method.
     * 
     * @link http://php.net/manual/en/function.openssl-get-cipher-methods.php Available methods.
     * @param string $cipherMethod
     */
    public function setCipherMethod($cipherMethod)
    {
        $this->encryptMethod = $cipherMethod;
    }// setCipherMethod


}

test-js.php

<?php
$nonceValue = 'nonce_value';// use nonce that generated while using OAuth.

$readableString = 'asdf-ghjk-qwer-tyui';
$encryptedString = 'eyJjaXBoZXJ0ZXh0IjoiNkRuSzRueVR5aERIQTVCdkF6SU9Mc0E0S1llUW5tZndvS0hIbERRMlE1VT0iLCJpdiI6IjNlNGU0YjFlNTBjNGRmODc2ZWExZTg3NjY3MDc4ZjBkIiwic2FsdCI6IjY0OWUxZDQ0NGNiZDc1YjBhODk2NmY2YTRjZTNjYzUzMmIyYTA4ZDQzZjlmYTQzNDRiOGU2MDFmNWIxODlkNzFjZGE3ZDc1YzU1YTBjMzNhMmM1ZWRlMjc5MTMxZTM5ZjNhYjgzY2JjNGQ5ZjIwYmY5YWE3YjdjN2MwNmVlMTZmNjJmYWEzMWU1MjFiMWZjNWFmZDcxMmRlNDQ3MWEyOTg3MDM0MzliODk0N2E0NGViOTMyMWFlMzI0ZWM2Zjg1ZjkwYmQzYzRmNjk5YzdmN2ViMTVhOGE0ZWExYjU1OGJmNWFiYjg5MzFjMjA5YTkzMWEwY2Q1NWM1NTgxMTRkNTY5NTIzZTk5OWMwZDA4Y2FiYmY4MzAzMTA0MzJkNzE2NmJlMDZlYzk3NjQzNzY1MzQ2NDI4YTM0ODM3MWUyOWRkNDU2ZTVmOGQ0NDgxZGVmZjY4M2FlOGYwOTJjODk3NjdhMzRhN2I0MWNlM2VlMDVlOWQ2ZDg4ZDI5MzVmZGM5MDUxY2VlZDhiYjllZDM5MzNjNjg2ODczZGNiOTJhZWI2MzBkMjNjODNhMjIyNTRjZDkxMDg4OTc4OWQ1MTI1MTc2MjQ2ZGYwOTQyODE5MTZlMmY4Y2RjYTU2MDEwMzEzZTM2NmE2ZDMyOTA4OGM3NzI5MWY3NDE3ODRiNTdmNTc1IiwiaXRlcmF0aW9ucyI6OTk5fQ==';
?>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <link rel="stylesheet" href="style.css">
    </head>
    <body>
    	<div class="resultPlaceholder"></div>

        <script src="https://code.jquery.com/jquery-3.3.1.min.js"></script>
        <script src="crypto-js.js"></script><!-- https://github.com/brix/crypto-js/releases crypto-js.js can be download from here -->
        <script src="Encryption.js"></script>
        <script>
            var readableString = '<?php echo $readableString; ?>';
            var nonceValue = '<?php echo $nonceValue; ?>';
            var encryptedString = '<?php echo $encryptedString; ?>';

            // on page loaded.
            jQuery(document).ready(function($) {
                let encryption = new Encryption();
                var encrypted = encryption.encrypt(readableString, nonceValue);
                console.log(encrypted);

                var decrypted = encryption.decrypt(encrypted, nonceValue);
                console.log(decrypted);

                var decryptedOldString = encryption.decrypt(encryptedString, nonceValue);
                console.log(decryptedOldString);

        	
                $('.resultPlaceholder').html('readable string: '+readableString+'<br>');
                $('.resultPlaceholder').append('encrypted: '+encrypted+'<br>');
                $('.resultPlaceholder').append('decrypted: '+decrypted+'<br>');
                $('.resultPlaceholder').append('decrypted from old encrypted string: <strong>'+decryptedOldString+'</strong><br>');
            });
        </script>
    </body>
</html>

test-php.php

<?php
require 'Encryption.php';

$nonceValue = 'nonce_value';// use nonce that generated while using OAuth.

$readableString = 'asdf-ghjk-qwer-tyui';
$encryptedString = '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';
?>
<!DOCTYPE html>
<html>
    <head>
        <meta charset="utf-8">
        <link rel="stylesheet" href="style.css">
    </head>
    <body>
        <?php 
        echo 'readable string: ' . $readableString . '<br>';
        $Encryption = new Encryption();
        $encrypted = $Encryption->encrypt($readableString, $nonceValue);
        echo 'encrypted: ' . $encrypted . '<br>';
        
        echo "\n\n\n";
        echo '<hr>';
        echo "\n\n\n";
        
        $decrypted = $Encryption->decrypt($encrypted, $nonceValue);
        echo 'decrypted: ' . $decrypted . '<br>';
        $decrypted = $Encryption->decrypt($encryptedString, $nonceValue);
        echo 'decrypted from old encrypted string: <strong>' . $decrypted . '</strong><br>';
        ?>
	</body>
</html>