storage.php

<?php
class StorageClass
{
	function __construct() {
		if( !isset($_SESSION) ){
        	$this->init_session();
    	}
   	}

   	public function init_session(){
    	session_start();
	}

    public function getSession() {
    	return $_SESSION['oauth2'];
    }

 	public function startSession($token, $secret, $expires = null)
	{
       	session_start();
	}

	public function setToken($token, $expires = null, $tenantId, $refreshToken, $idToken)
	{
	    $_SESSION['oauth2'] = [
	        'token' => $token,
	        'expires' => $expires,
	        'tenant_id' => $tenantId,
	        'refresh_token' => $refreshToken,
	        'id_token' => $idToken
	    ];
	}

	public function getToken()
	{
	    //If it doesn't exist or is expired, return null
	    if (empty($this->getSession())
	        || ($_SESSION['oauth2']['expires'] !== null
	        && $_SESSION['oauth2']['expires'] <= time())
	    ) {
	        return null;
	    }
	    return $this->getSession();
	}

	public function getAccessToken()
	{
	    return $_SESSION['oauth2']['token'];
	}

	public function getRefreshToken()
	{
	    return $_SESSION['oauth2']['refresh_token'];
	}

	public function getExpires()
	{
	    return $_SESSION['oauth2']['expires'];
	}

	public function getXeroTenantId()
	{
	    return $_SESSION['oauth2']['tenant_id'];
	}

	public function getIdToken()
	{
	    return $_SESSION['oauth2']['id_token'];
	}

	public function getHasExpired()
	{
		if (!empty($this->getSession()))
		{
			if(time() > $this->getExpires())
			{
				return true;
			} else {
				return false;
			}
		} else {
			return true;
		}
	}
}
?>