Unable to get oAuth token for BigCommerce once click app - php

Question

I am a complete noob to BigCommerce as well as plugins. And recently planned to develop a one click app which could be installed by the users of any store on their store. I have good hand on php. So, i can code but dont know the flow for plugins.
To create a draft app i went to devtools.bigcommerce.com and created an app defined Auth Callback url as https://amanangira.com/bCommerce/oauth.php
and Load Callback url as https://amanangira.com/bCommerce/callBack.php
in oauth.php i inserted the following code
<?php
$data = array( "client_id" => "123456789",
"client_secret" => "123456789",
"redirect_uri" => "https://amanangira.com/bCommerce/callBack.php",
"grant_type" => "authorization_code",
"code" => $_GET["code"], "scope" => $_REQUEST["scope"], "context" => $_GET["context"], );
$postfields = http_build_query($data);
$ch = curl_init();
//$url = "https://api.bigcommerce.com/stores/wky4s3lfef/v3/";
$url = "https://login.bigcommerce.com/oauth2/token";
curl_setopt($ch, CURLOPT_URL,$url);
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch,CURLOPT_HTTPHEADER,array('Content-Type: application/x-www-form-urlencoded'));
curl_setopt($ch, CURLOPT_POSTFIELDS, $postfields);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
$output = curl_exec ($ch);
curl_close ($ch);
$obj = json_decode($output);
var_dump($obj);
?>
Now whenever i install the app in my test store it says following.
/var/www/html/angira/bCommerce/oauth.php:37:
object(stdClass)[3]
public 'error' => string 'redirect_uri_mismatch' (length=21)
public 'error_description' => string 'Parameter redirect_uri does not match registered URI' (length=52)
Please help with the above in as much as simple terms.
Thank you.

Answer 1

After some hit and trials and i finally stumbled upon the solution. Which was to update the redirect_uri in the oauth.php to that which was the Auth Callback uri in the application configuration.
"redirect_uri" => "https://amanangira.com/bCommerce/oauth.php"