Class method that gets an authenitcation token from BigCommerce

get_remote_auth_token.php

    /*
     * Get the auth token from BigCommerce
     *
     * @access public
     * @return string $token
     */
    public function get_remote_auth_token() {

        // Set up the REST authentication headers
        $headers[ 'X-Auth-Token' ]  = $this->access_token;
        $headers[ 'X-Auth-Client' ] = $this->client_id;
        $headers[ 'content-type' ]  = 'application/json';

        // The token needs an expiration. You can either set it short
        // and manage recreation, or set it very long and never change
        // Regardless it needs to be a UTC timestamp
        $expires = date('U') + 100000000;

        // Set up the query to get the token. Formatted in JSON, requires
        // the channel ID, the expiration, and CORS allowance.
        $query = '
            {
              "channel_id": ' . $this->channel_id . ',
              "expires_at": ' . $expires . ',
              "allowed_cors_origins": [
                "' . get_home_url() . '"
              ]
            }
        ';

        // set up the POST args
        $args[ 'method']  = 'POST';
        $args[ 'headers'] = $headers;
        $args[ 'body' ]   = $query;

        // The request gets sent to the token API endpoint with your
        // store hash in the URL.
        $url = 'https://api.bigcommerce.com/stores/' . $this->store_hash . '/v3/storefront/api-token';

        // send the query
        $request = wp_safe_remote_post( $url, $args );

        // get the body out of the result
        $body = json_decode( $request['body'] );

        // get the token out of the body
        $token = $body->data->token;

        return $token;

    }