我是一个新的理解编码语言，并已开始学习使用wordpress的东西。我正在尝试集成一个支付网关，可以生成access\ u token和refresh\ u token，我需要将它们存储到我的数据库中，以便为支付和用户数据更新进行进一步的api调用。
下面是我用来生成令牌的代码。请帮助了解如何在数据库中存储令牌值。我尝试复制wordpress寄存器代码以插入值，但未能成功。

<?php
    session_start();
    include_once "page-signup.php";

    $curl = curl_init();
    curl_setopt_array($curl, array(
    CURLOPT_URL => "https://test.instamojo.com/oauth2/token/",
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_ENCODING => "",
    CURLOPT_MAXREDIRS => 10,
    CURLOPT_TIMEOUT => 30,
    CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
    CURLOPT_CUSTOMREQUEST => "POST",
    CURLOPT_POSTFIELDS =>  
    "client_id=gC4z8rBV55SDiavZobpvZCcanwK3mbnY
    &client_secret=dYFbCXaX9WUy1c3kkCXV8JRJkTxmLcxCXwncVKWlWsh8c0QOI
    5Uz30PCzOieC879RT7PLsEwrRKZDvZXqYpF5fZiE2Z62z3dly7p7ZUbGHTmOWmBsh3
    &grant_type=password
    &username=$username
    &password=$password",
    CURLOPT_HTTPHEADER => array(
    "Cache-Control: no-cache",
    "Content-Type: application/x-www-form-urlencoded",
      ),
      ));
    $response = curl_exec($curl);
    $err = curl_error($curl);

    curl_close($curl);

    if ($err) {
    echo "cURL Error #:" . $err;
        } else {

    $json_decode=json_decode($response,true);
    $refresh_token=$json_decode['refresh_token'];
    $access_token=$json_decode['access_token'];
      }

    echo $response;

     ?>