api.php

<?php
class API {

    private $token;
    private $tokenExpiry;

    public function __construct()
    {

        $this->deserializeToken();

        if ($this->tokenNeedsUpdating()) {
            $this->requestToken();
        }

    }

    /**
     * Pulls the token from the session into the object.
     *
     * @return null
     **/
    public function deserializeToken()
    {
        $this->token = session('token', false);
        $this->tokenExpirey = session('tokenExpiry', false);
    }

    /**
     * Returns whether or not the token needs updating.
     *
     * @return bool
     **/
    public function tokenNeedsUpdating()
    {
        if (!$this->token || !$this->tokenExpiry){
            return true;
        }

        if (time() > $this->tokenExpiry){
            return true;
        }

        return false;
    }

    /**
     * Requests a new token with the give username/password, then deserializes it.
     *
     * @return null
     **/
    public function requestToken()
    {
        // do API call

        // put in session

        session('tokenExpire', $this->guessTokenExpiry());

        $this->deserializeToken();

    }

}