<?php 

step 1 : hit in browser
https://login.microsoftonline.com/f71f3593-1e98-410a-9a9c-bb7efc4753d4/oauth2/v2.0/authorize?
client_id=c1829db3-0d81-4e90-ba47-23f7cde40118
&response_type=code
&redirect_uri=https://fcsus.com/email/php_plugins/php-imap/mail_cred.php
&scope=https://graph.microsoft.com/.default%20offline_access


step 2 : get code from response from above and used into access.php
after that call access.php will get refresh token which need to change into gvs_cf.php at shell on server

access.php code as below 

client secret is value 
Teatant id from app where clinet id 


<?php

$CLIENT_ID="c1829db3-0d81-4e90-ba47-23f7cde40118";
$CLIENT_SECRET="914e0bec-3889-478c-9ecf-21eb49c24734";
$TENANT="KFc8Q~3-8v~Abi6lHblIRaUxf1Q-Yk1IUoAlQbS0";
$SCOPE="https://outlook.office365.com/IMAP.AccessAsUser.All offline_access";
$CODE="0.AVsAkzUf95geCkGanLt-_EdT1LOdgsGBDZBOukcj983kARhbAPE.AgABAAIAAAD--DLA3VO7QrddgJg7WevrAgDs_wUA9P96-cyrecsYHqOQSI33ughV7oTAos1BnKIGiX-IqTBWsSm3tKOuqWMwn7zOCr15ZkBvmeACvBuV3zjRQsROYc8JKgr_GeEH3Wvy3ZDpZtPduEBBgXtTpRcJ8HGht6xnSULPkHygJOHVKaDSB28k_3dqQWUDLgM-rqv_HLcnfxn0zBcL-G8KecfnEw0zgXlH4apVNWpkWKmOFf9DZmPsGhoP8EjE9Uwp0pia97a3ep3s3meeBzYg79Uv_7YCJxUexjONJvJIrdmqBwxWKTeym8D0ZJrTvewj_wdgBdzxcWZ_iYF_QmbsLCrYOi0knDOcwXtHVTHkFanyz_f6UPUcwVCLGqny2T9cmOGy84DMUIgkHkXjbVooWjqFIw8FGO3ADVSqeNAs5MO8yFf47XhgJkYCHaAG5FpMg47h0qLqvdwULducE7KoSP-1fmCjCHsXYlleS0u_gzC1Xzv4V5RcIygTXe8Kdi3KYLfnm83yxg6lQJK0nbxsRYQym_OvFJevWvj5wuQnMS22uRpU5dk51j1eJLM22e176tFIz7fZ16HJr7GCmPmdCNFZ_-mZFmhlsNxLz6suv2u6ZtaEerHA3J66yTiSrv5wsL8gmdtUWhVVOpkcJphaYFw3K1L0ViysABy0uGmzC1Uz5SXXjbmk74ejSt5Zit9M3SrGnkPazN6hE_-QYUph9rBptq9yzwCjyy1dJWe69ewYpHG5wKL1jCt1R5QKnfT3-dw";
$SESSION="28726aef-11f5-422b-80cf-0ab4981ba74d";
$REDIRECT_URI="https://email.greatvaluestores.com/applications/php_plugins/php-imap/mail_cred.php";

echo "Trying to authenticate the session..";

$url= "https://login.microsoftonline.com/$TENANT/oauth2/v2.0/token";

$param_post_curl = [ 
 'client_id'=>$CLIENT_ID,
 'scope'=>$SCOPE,
 'code'=>$CODE,
 'session_state'=>$SESSION,
 'client_secret'=>$CLIENT_SECRET,
 'redirect_uri'=>$REDIRECT_URI,
 'grant_type'=>'authorization_code' ];

$ch=curl_init();
curl_setopt($ch,CURLOPT_URL,$url);
curl_setopt($ch,CURLOPT_POSTFIELDS, http_build_query($param_post_curl));
curl_setopt($ch,CURLOPT_POST, 1);
curl_setopt($ch,CURLOPT_RETURNTRANSFER, true);

$oResult=curl_exec($ch);

echo "result : \n";

var_dump($oResult);


?>