Based on the generic example doc.
<?php
require dirname(__FILE__, 2) . '/vendor/autoload.php';
$disco_url = 'https://www.dropbox.com/.well-known/openid-configuration';
$client_id = 'yourClient_id';
$session_key = 'YWQ4Q1Hpb_zQliS5wGYDDPZm2xC7PzyfjgLKBNodkazkN_pEPlm7yVBw5r9_pDzSwHJRsFVZShQyb_LFUSMBGQ';
$callback_url = 'https://yourAPPurl/callback.php';
$client = new Svgta\OidcClient\init($disco_url, $client_id);
$client->setSessionKey($session_key);
$auth = $client->authorization($callback_url);
$auth->addScope('email profile');
$auth->set_state();
$auth->exec();
You can not get userInfo from an userInfo enpoint. You can get some informations from the id_token directly.
<?php
require dirname(__FILE__, 2) . '/vendor/autoload.php';
$disco_url = 'https://www.dropbox.com/.well-known/openid-configuration';
$client_id = 'yourClient_id';
$client_secret = 'yourClient_secret';
$session_key = 'YWQ4Q1Hpb_zQliS5wGYDDPZm2xC7PzyfjgLKBNodkazkN_pEPlm7yVBw5r9_pDzSwHJRsFVZShQyb_LFUSMBGQ';
$client = new Svgta\OidcClient\init($disco_url, $client_id, $client_secret);
$client->setSessionKey($session_key);
$tokenRes = $client->token();
$tokens = $tokenRes->get_tokens();
$userInfo = $tokensRes->get_id_token_payload();