Decrypt laravel_session outside of the Laravel app. This is just a proof of concept, cleanup and extend to your needs.

decrypt-laravel-session.php

<?php

    function decrypt_laravel_session() {
        # Method 1. Autload Laravel into the application.
        require '/home/vagrant/Code/minside-fjordclub/webroot/bootstrap/autoload.php';
        $app = require_once '/home/vagrant/Code/minside-fjordclub/webroot/bootstrap/app.php';
        $app->make('Illuminate\Contracts\Http\Kernel')->handle(Illuminate\Http\Request::capture());
        $id = (isset($_COOKIE[$app['config']['session.cookie']]) ? $app['encrypter']->decrypt($_COOKIE[$app['config']['session.cookie']]) : null);

        if ($id)
        {
            $app['session']->driver()->setId($id);
            $app['session']->driver()->start();

            $user_id = $app['auth']->driver()->getSession()->get('id');
        }


        # Method 2. Replicate the Laravel Decrypt code.
        include('includes/laravel/LaravelCookieDecrypter.php');
        $laravel_cookie_decrypter = new LaravelCookieDecrypter();
        $session_id = $laravel_cookie_decrypter->decrypt($_COOKIE['laravel_session']); // Returns the session_id
        // Require the session from the database/filesystem/cache etc with the session_id
    }

LaravelCookieDecrypter.php

<?php

class LaravelCookieDecrypter {

    /**
     * The encryption key.
     *
     * @var string
     */
    protected $key = 'YOUR LARAVEL .ENV APP KEY';

    /**
     * The algorithm used for encryption.
     *
     * @var string
     */
    protected $cipher = MCRYPT_RIJNDAEL_128;

    /**
     * The mode used for encryption.
     *
     * @var string
     */
    protected $mode = MCRYPT_MODE_CBC;

    /**
     * The block size of the cipher.
     *
     * @var int
     */
    protected $block = 16;

    protected $stringUtils;

    /**
     * LaravelCookieDecrypter constructor.
     */
    public function __construct()
    {
        require_once('SecureRandom.php');
        require_once('StringUtils.php');
    }


    public function decrypt($payload)
    {
        $payload = $this->getJsonPayload($payload);

        // We'll go ahead and remove the PKCS7 padding from the encrypted value before
        // we decrypt it. Once we have the de-padded value, we will grab the vector
        // and decrypt the data, passing back the unserialized from of the value.
        $value = base64_decode($payload['value']);

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

        return unserialize($this->stripPadding($this->mcryptDecrypt($value, $iv)));
    }



    protected function getJsonPayload($payload)
    {
        $payload = json_decode(base64_decode($payload), true);

        // If the payload is not valid JSON or does not have the proper keys set we will
        // assume it is invalid and bail out of the routine since we will not be able
        // to decrypt the given value. We'll also check the MAC for this encryption.
        if ( ! $payload || $this->invalidPayload($payload))
        {
            var_dump('Invalid data.');
        }

        if ( ! $this->validMac($payload))
        {
            var_dump('MAC is invalid.');
        }

        return $payload;
    }


    protected function validMac(array $payload)
    {
        $bytes = (new SecureRandom)->nextBytes(16);

        $calcMac = hash_hmac('sha256', $this->hash($payload['iv'], $payload['value']), $bytes, true);

        return StringUtils::equals(hash_hmac('sha256', $payload['mac'], $bytes, true), $calcMac);
    }

    protected function stripPadding($value)
    {
        $pad = ord($value[($len = strlen($value)) - 1]);

        return $this->paddingIsValid($pad, $value) ? substr($value, 0, $len - $pad) : $value;
    }



    protected function mcryptDecrypt($value, $iv)
    {
        try
        {
            return mcrypt_decrypt($this->cipher, $this->key, $value, $this->mode, $iv);
        }
        catch (Exception $e)
        {
            var_dump($e->getMessage());
            die;
        }
    }


    protected function invalidPayload($data)
    {
        return ! is_array($data) || ! isset($data['iv']) || ! isset($data['value']) || ! isset($data['mac']);
    }

    protected function paddingIsValid($pad, $value)
    {
        $beforePad = strlen($value) - $pad;

        return substr($value, $beforePad) == str_repeat(substr($value, -1), $pad);
    }


    protected function hash($iv, $value)
    {
        return hash_hmac('sha256', $iv.$value, $this->key);
    }


}

SecureRandom.php

<?php

/*
 * This file is part of the Symfony package.
 *
 * (c) Fabien Potencier <[email protected]>
 *
 * For the full copyright and license information, please view the LICENSE
 * file that was distributed with this source code.
 */


/**
 * A secure random number generator implementation.
 *
 * @author Fabien Potencier <[email protected]>
 * @author Johannes M. Schmitt <[email protected]>
 */
class SecureRandom
{
    private $useOpenSsl;
    private $seed;
    private $seedUpdated;
    private $seedLastUpdatedAt;
    private $seedFile;

    /**
     * Constructor.
     *
     * Be aware that a guessable seed will severely compromise the PRNG
     * algorithm that is employed.
     *
     * @param string          $seedFile
     */
    public function __construct($seedFile = null)
    {
        $this->seedFile = $seedFile;

        // determine whether to use OpenSSL
        if ('/' === DIRECTORY_SEPARATOR && PHP_VERSION_ID < 50304) {
            $this->useOpenSsl = false;
        } elseif (!function_exists('openssl_random_pseudo_bytes')) {
            $this->useOpenSsl = false;
        } else {
            $this->useOpenSsl = true;
        }
    }

    /**
     * {@inheritdoc}
     */
    public function nextBytes($nbBytes)
    {
        // try OpenSSL
        if ($this->useOpenSsl) {
            $bytes = openssl_random_pseudo_bytes($nbBytes, $strong);

            if (false !== $bytes && true === $strong) {
                return $bytes;
            }
        }

        // initialize seed
        if (null === $this->seed) {
            if (null === $this->seedFile) {
                throw new \RuntimeException('You need to specify a file path to store the seed.');
            }

            if (is_file($this->seedFile)) {
                list($this->seed, $this->seedLastUpdatedAt) = $this->readSeed();
            } else {
                $this->seed = uniqid(mt_rand(), true);
                $this->updateSeed();
            }
        }

        $bytes = '';
        while (strlen($bytes) < $nbBytes) {
            static $incr = 1;
            $bytes .= hash('sha512', $incr++.$this->seed.uniqid(mt_rand(), true).$nbBytes, true);
            $this->seed = base64_encode(hash('sha512', $this->seed.$bytes.$nbBytes, true));
            $this->updateSeed();
        }

        return substr($bytes, 0, $nbBytes);
    }

    private function readSeed()
    {
        return json_decode(file_get_contents($this->seedFile));
    }

    private function updateSeed()
    {
        if (!$this->seedUpdated && $this->seedLastUpdatedAt < time() - mt_rand(1, 10)) {
            file_put_contents($this->seedFile, json_encode(array($this->seed, microtime(true))));
        }

        $this->seedUpdated = true;
    }
}

StringUtils.php

<?php

class StringUtils
{
    /**
     * This class should not be instantiated.
     */
    private function __construct()
    {
    }

    /**
     * Compares two strings.
     *
     * This method implements a constant-time algorithm to compare strings.
     * Regardless of the used implementation, it will leak length information.
     *
     * @param string $knownString The string of known length to compare against
     * @param string $userInput   The string that the user can control
     *
     * @return bool true if the two strings are the same, false otherwise
     */
    public static function equals($knownString, $userInput)
    {
        // Avoid making unnecessary duplications of secret data
        if (!is_string($knownString)) {
            $knownString = (string) $knownString;
        }

        if (!is_string($userInput)) {
            $userInput = (string) $userInput;
        }

        if (function_exists('hash_equals')) {
            return hash_equals($knownString, $userInput);
        }

        $knownLen = self::safeStrlen($knownString);
        $userLen = self::safeStrlen($userInput);

        if ($userLen !== $knownLen) {
            return false;
        }

        $result = 0;

        for ($i = 0; $i < $knownLen; ++$i) {
            $result |= (ord($knownString[$i]) ^ ord($userInput[$i]));
        }

        // They are only identical strings if $result is exactly 0...
        return 0 === $result;
    }

    /**
     * Returns the number of bytes in a string.
     *
     * @param string $string The string whose length we wish to obtain
     *
     * @return int
     */
    public static function safeStrlen($string)
    {
        // Premature optimization
        // Since this cannot be changed at runtime, we can cache it
        static $funcExists = null;
        if (null === $funcExists) {
            $funcExists = function_exists('mb_strlen');
        }

        if ($funcExists) {
            return mb_strlen($string, '8bit');
        }

        return strlen($string);
    }
}