Facebook API redirect_ui error - php

Question

I'm implementing a new app that uses Facebook login:
On developers.facebook.com I set the Settings:
App Domains: (empty)
Site URL: http://localhost/site/
Client OAuth Login: Yes
Web OAuth Login: Yes
Force Web OAuth Reauthentication: No
Embedded Browser OAuth Login: No
Valid OAuth redirect URIs: http://localhost/site/externallogin/
And in my app the login link:
$facebook = new Facebook\Facebook([
'app_id' => FB_APP_ID,
'app_secret' => FB_APP_SECRET,
'default_graph_version' => 'v2.5',
]);
$helper = $facebook->getRedirectLoginHelper();
$permissions = ['email', 'public_profile', 'user_friends'];
$loginUrl = $helper->getLoginUrl("http://localhost/site/externallogin", $permissions);
echo 'Log in with Facebook!<hr>';
And my externallogin page:
$helper = $facebook->getRedirectLoginHelper();
try {
$accessToken = $helper->getAccessToken();
} catch(Facebook\Exceptions\FacebookResponseException $e) {
// When Graph returns an error
echo 'Graph returned an error: ' . $e->getMessage();
exit;
} catch(Facebook\Exceptions\FacebookSDKException $e) {
// When validation fails or other local issues
echo 'Facebook SDK returned an error: ' . $e->getMessage();
exit;
}
But When I'm redirect I got the following error:
Graph returned an error: Error validating verification code. Please
make sure your redirect_uri is identical to the one you used in the
OAuth dialog request
I've tried to change default_graph_version to 2.2, change the Valid OAuth redirect URIs and the return url to all kinds, but nothing, the same.
I've read everything related with this and tried all the approach, but still the same.
I don't know what can be causing this error.
My question is: How can I fix this error I get the the access token correctly.
print 1
print 2

Answer 1

The page $helper->getAccessToken() runs on must be the exact same URL you provide to $helper->getLoginUrl(). As you've indicated http://localhost/site/externallogin redirects to http://localhost/site/externallogin/ on your webserver, add the / when you make $loginUrl:
$loginUrl = $helper->getLoginUrl("http://localhost/site/externallogin/", $permissions);